What is the cloud

When tech companies say your data is in the cloud, or that you can work in the cloud, it has nothing to do with white fluffy things in the sky. It has a terrestrial home. The cloud refers to software and services that run on the Internet, instead of locally on your computer.

Most cloud services can be accessed through a Web browser like Firefox or Google Chrome, and some companies offer dedicated mobile apps. The advantage of the cloud is that you can access your information on any device with an Internet connection.

Colleagues can even collaborate on the same document. But the cloud has its downfalls, too. The same applies if there are any technical issues or outages on the server side. Our mission has never been more vital than it is in this moment: to empower through understanding. Financial contributions from our readers are a critical part of supporting our resource-intensive work and help us keep our journalism free for all. But there are also web applications —or web apps —that run in the cloud and do not need to be installed on your computer.

Many of the most popular sites on the Internet are actually web apps. You may have even used a web app without realizing it! Let's take a look at some popular web apps. Computer Basics: Understanding the Cloud. Next: Keeping Your Computer Clean. Companies can control exactly where their data is being held and can build the infrastructure in a way they want -- largely for IaaS or PaaS projects -- to give developers access to a pool of computing power that scales on-demand without putting security at risk.

However, that additional security comes at a cost, as few companies will have the scale of AWS, Microsoft or Google, which means they will not be able to create the same economies of scale. Still, for companies that require additional security, private cloud may be a useful stepping stone, helping them to understand cloud services or rebuild internal applications for the cloud, before shifting them into the public cloud.

Cloud computing is insatiably gobbling up more of the backend services that power businesses. But, some companies have apps with privacy, security, and regulatory demands that preclude the cloud. Here's how to find the right mix of public cloud and private cloud. Hybrid cloud is perhaps where everyone is in reality: a bit of this, a bit of that.

Some data in the public cloud, some projects in private cloud, multiple vendors and different levels of cloud usage.

According to research by TechRepublic, the main reasons for choosing hybrid cloud include disaster recovery planning and the desire to avoid hardware costs when expanding their existing data center. For start-ups who plan to run all their systems in the cloud getting started is pretty simple.

But the majority of companies it is not so simple: with existing applications and data they need to work out which systems are best left running as they, and which to start moving them to cloud infrastructure. This is a potentially risky and expensive move, and migrating to the cloud could cost companies more if they underestimate the scale of such projects. A survey of businesses that were early cloud adopters found that the need to rewrite applications to optimise them for the cloud was one of the biggest costs, especially if the apps were complex or customised.

A third of those surveyed said cited high fees for passing data between systems as a challenge in moving their mission-critical applications. The report by Forrester also found that the skills required for migration are both difficult and expensive to find -- and that even when organisations could find the right people they risked them being stolen away by cloud computing vendors with deep pockets.

One third of those surveyed said their software database license costs drastically increased if they moved applications. Beyond this the majority also remained worried about the performance of critical apps and one in three cited this as a reason for not moving some critical applications. Actually it turns out that is where the cloud really does matter; indeed geopolitics is forcing significant changes on cloud computing user and vendors.

Firstly, there is the issue of latency: if the application is coming from a data center on the other side of the planet, or on the other side of a congested network, then you may find it sluggish compared to a local connection.

That's the latency problem. Secondly, there is the issue of data sovereignty. Many companies -- particularly in Europe -- have to worry about where their data is being processed and stored. European companies are worried that, for example, if their customer data is being stored in data centers in the US or owned by US companies it could be accessed by US law enforcement. As a result the big cloud vendors have been building out a regional data center network so that organizations can keep their data in their own region.

In Germany, Microsoft has gone one step further, offering its Azure cloud services from two data centers , which have been set up to make it much harder for US authorities -- and others -- to demand access to the customer data stored there.

The customer data in the data centers is under the control of an independent German company which acts as a "data trustee", and Microsoft cannot access data at the sites without the permission of customers or the data trustee. Expect to see cloud vendors opening more data centers around the world to cater to customers with requirements to keep data in specific locations.

And regulation of cloud computing varies widely elsewhere across the world: for example AWS recently sold a chunk of its cloud infrastructure in China to its local partner because of China's strict tech regulations. Cloud security is another issue; the UK government's cyber security agency has warned that government agencies need to consider the country of origin when it comes to adding cloud services into their supply chains.

While it was warning about antivirus software in particular, the issue is the same for other types of services too. Consultants Accenture have warned that ' digital fragmentation ' is the result as different countries enact legislation to protect privacy and improve cyber security. While the aims of the laws is laudable, the impact is to raise costs for businesses.

Three quarters of the CIOs and CTOs surveyed expect to exit a geographic market, delay their market-entry plans or abandon market-entry plans in the next three years as a result of increased barriers to globalization. AWS: The complete business guide to Amazon's cloud services. Cloud computing services are operated from giant datacenters around the world. AWS divides this up by 'regions' and 'availability zones'. An AZ is composed of one or more datacenters that are far enough apart that in theory a single disaster won't take both offline, but close enough together for business continuity applications that require rapid failover.

Google uses a similar model , dividing its cloud computing resources into regions which are then subdivided into zones, which include one or more datacenters from which customers can run their services. It currently has 15 regions made up of 44 zones: Google recommends customers deploy applications across multiple zones and regions to help protect against unexpected failures.

Microsoft Azure divides its resources slightly differently. It offers regions which it describes as is a "set of datacentres deployed within a latency-defined perimeter and connected through a dedicated regional low-latency network". It also offers 'geographies' typically containing two or more regions, that can be used by customers with specific data-residency and compliance needs "to keep their data and apps close".

It also offers availability zones made up of one or more data centres equipped with independent power, cooling and networking. Those data centers are also sucking up a huge amount of power: for example Microsoft recently struck a deal with GE to buy all of the output from its new megawatt wind farm in Ireland for the next 15 years in order to power its cloud data centers.

When it comes to IaaS and PaaS there are really only a few giant cloud providers. While the following pack might be growing fast, their combined revenues are still less than those of AWS, according to data from the Synergy Research Group. These big players will dominate the delivery of cloud services: Gartner said two thirds of the spending on cloud computing services will go through the top 10 public cloud providers through to It's also worth noting that while all these companies are selling cloud services, they have different strengths and priorities.

Microsoft in contrast has a particular emphasis on SaaS thanks to Office and its other software largely aimed at end user productivity, but is also trying to rapidly grow its IaaS and Paas offering through Azure.

IBM and Oracle's cloud businesses are also made up of a combination of Saas and more infrastructure based offerings. There are vast numbers of companies who have are offering applications through the cloud using a SaaS model. Salesforce is probably the best known of these. The cloud giants have different strengths. While AWS and Microsoft's commercial cloud businesses are about the same size, Microsoft includes Office in its figures.

The challenger in any competitive market has greater incentive to produce sharper and more customer-focused products and services. Increasingly the major cloud computing vendors are attempting to differentiate according to the services that they offer, especially if they can't compete with AWS and Microsoft in terms of scale.

Google for example is promoting its expertise around artificial intelligence; Alibaba wants to attract customers who are interested in learning from its retail know-how.

In a world where most companies will use at least one cloud provider and usually many more, IBM wants to position itself as the company that can manage all these multiple clouds. Meanwhile AWS is pitching itself as the platform for builders , which is its new take on developers.

The cost of some cloud computing services -- particularly virtual machines -- has been falling steadily thanks to continued competition between these big players. There is some evidence that the price cuts may spread to other services like storage and databases, as cloud vendors want to win the big workloads that are moving out of enterprise datacenters and into the cloud.

That's likely to be good news for customers and prices could still fall further, as there remains a hefty margin in even the most commodity areas of cloud infrastructure services, like provision of virtual machines.