The Raspberry Pi is a tiny computer that was developed in the UK for educational purposes. Some details of the development are described here.
After waiting several months for delivery, my Raspberry Pi finally arrived in July 2012. To get it going I bought a whole lot of gear including:
only to find I needed none of that stuff.
As shown in the photo to the left, all you need is:
Then you can run the Raspberry Pi in headless mode from another
computer on the network.
This was a huge relief because using the TV in the family room was impractical and I couldn't figure out how I was going to justify buying a TV just for the Raspberry Pi.
The large SD card enables you to store lots of programs and some data - it's equivalent to the hard-disk in a laptop or desktop.
There is a wealth of information on setting up a Raspberry Pi on the web. I found the offical Raspberry Pi forum here very helpful. To get to the forum from that webpage, you need to click the box with lines in the top right corner and navigate from there.