Do I even need to explain this one? This is the entire package of the original game, for each of them, giving you episodes 1-3 of the original game, Thy Flesh Consumed from Ultimate Doom, and of course, Doom II, when hell makes it back to earth, after you kicked its collective butt.
Here you are folks, enjoy again, and if you somehow missed this due to lack of age or being locked in some sort of facility, catch up! This is where first person shooting became what it is. (Ok here's a shameless plug for marathon too...)
P.S. If you truly want to experience the old school Doom and Doom II in a completely different way, including multiplayer servers that still exist and are populated, (i played just last night against 5 other people, yes 5, in a random pick up match) then google Skulltag Doom after downloading this package.