There are a few different versions of the Raspberry Pi, each made for different uses. All of the current versions use a microSD card for the operating system and file storage. They are powered by a micro-USB port, have one HDMI port, one audio/video jack socket, and a 40-pin GPIO connector. This is a list of the current versions of the Raspberry Pi and their features.
Model A+: The Model A+ is cheaper, smaller and has fewer connectors than the other versions of the Raspberry Pi. It is made for use in small, low-power projects. It features a single-core 700 MHz ARM processor, 256MBs of RAM and one USB port.
Model B+: The Model B+ is more expensive than the Model A+ and has more connectors and RAM. It features a single-core 700 MHz ARM processor, 512MBs of RAM, four USB ports and one Ethernet port.
Raspberry Pi 2, Model B: The Raspberry Pi 2 Model B is more expensive than the other versions of the Raspberry Pi and has much more RAM and a much faster processor. It features a quad-core 900MHz ARM processor, 1GB of RAM, four USB ports and one Ethernet port.
↑A computer that is all on a single printed circuit board with no removable parts or external parts needed to work.
↑The Raspberry Pi Foundation, "About Us". Retrieved on 21 July 2015
↑NOOBS stands for New Out Of Box Software. There are several choices of operating system available, including Arch Linux, OpenELEC (media center), Pidora (Fedora Linux remix), raspbmc (media center), Raspbian (recommended), and RISC OS (non-Linux).