This designates a whole series of similar computers. There where models called 400, 800, and 1200, and also variations with XE and XL. I don't know the details.
There are 123 games listed for Atari 8-bit in this list.
Adventureland was created by Hans Persson and is now maintained by Stefan Meier.
If you find any errors or have information that is missing, please let me know