The Raspberry Pi is a Single Computer Board - developed to encourage and aid the teaching of programming and computing. It is also a fantastic starting point for the development of the Internet of Things (IoT) projects. The low cost and 'plug and play' nature of Pi makes for a board that is accessible to all and has numerous connectivity options.
Pi is the perfect experimental tool, whether you want to use it as a desktop computer, media centre, server or monitoring/security device within your home. No limits. Linux-based operating systems run on the Pi with plenty of access to free software and downloads.