>>132138
>which version(?)
Crispy Doom, the first one. The others are for different games that also run on the Doom engine. Crispy Doom is a port that you to run Doom on modern hardware, so you don't have to run the game in DOS/DOSBox. It also makes a few tweaks to make it more enjoyable. For example, you can rebind the controls so that you can look left and right using the mouse, and move with WASD. (Run Crispy-Setup to do this.)

>and iwads(???)
Iwads are the game's files, its code, graphics, and everything else that the port needs to run. Download the ones for The Ultimate Doom, Doom II, Plutonia and TNT. Put these in the folder where you installed Crispy Doom.