The Raspberry Pi is almost a throwback to the early days of computing [yes, I am old] when if you wanted the computer to do something, you designed the hardware and software yourself.
It is not a plug-and-play game machine. It is a bit slow. But that's okay. It wasn't designed to be a game machine, it is intended to be an inexpensive platform to help people learn about computers.
You have to download an operating system and burn it onto an SD card. The SD card then becomes the boot medium. The beastie will then happily function as a Linux computer, tho I think there is an Android port on the way.
It has both HDMI and composite video outputs. The HDMI can be connected to a dvi monitor with the appropriate cable. You must supply keyboard, mouse, and internet. I use a powered usb hub.
In short, it is a computer for folkes who want to learn the nuts and volts* of computers.
*That is the name of a magazine devoted to electronics hobbyists.