Here's a reminder of how the naming scheme is – good for a brush-up or new knowledge!
Get the big picture here
The Debian release cycle is not only long, but has always three different branches: stable, testing (occasionally frozen) and stable.
But when a newbie goes there for download things, he will also notice symlinks to other names, currently sarge, etch and sid.
He might also have heard that “Sarge” is “3.1″, “Woody” was “3.0″, and so on. What's this mess?