The Raspberry Pi is £15 computer that is the size of a credit card (despite it being made in Britain by a British company, the pi is actually priced in dollars, 25 of them to be precise, so the £ price might vary depending on exchange rates etc.) Though it is multipurpose and can be used for pretty much anything you can imagine, it is mainly targeted at children, to allow them to have a real computer that they can learn on.
Depending on your computer experience, the word computer might mean many different things to you, so telling you that the Raspberry Pi is one might not help a great deal. It also might not help if I tell you that the pi is fairly general purpose computer, so lets look at some specifics.
To a lot of people computer means a desktop computer that is used for surfing the web, editing spreadsheets etc., and a pi can definitely be used in this way with the addition of a keyboard, mouse and monitor.
They can also be used as servers. Servers are computers that other computers connect to and, as result, don’t need keyboards and monitors of their own. One common use of a pi is as a file server (also known as a NAS box). In this configuration, the pi is used as a central location to store files (such as backups, your music library, etc.) on your home network. These files can then be shared (assuming you have allowed it) with all the other computers (including mobile phones etc.) in your home and, if you wish, on the internet.
However, this is just the beginning. Computers crop up everywhere, from controlling your digital TV to the satellites in sky. And, thanks to its combination of USB ports and GPIO connector there are very few things that the pi can’t be programmed to control (including robots!)
So if you son/daughter/niece/nephew is in need of first computer, if you have a computer project round the home or office, if you are planning some cutting edge piece of robotics or if you just want to learn more about computers, the Raspberry Pi is an ideal choice. It is cheap, small and low power, has a fantastic community and is made by a charitable organisation, the Raspberry Pi Foundation, that is dedicated to empowering computer users by making computers fun and accessible. What more do you want? Go buy one now!