The 4th version of the Atari 2600 Platform, but the first to actually have the name Atari 2600, the previous ones being called the Atari VCS.
This model has 4 switches on the main control panel and a black case, as opposed to the previous models which sported a 70's woodgrain styling. Sometimes referred unofficially as the "Darth Vader" version because of the black case.