ADOM is a roguelike, in the tradition of NetHack but, IMHO, much better. It stands for Ancient Domains of Mystery
JADE is Java Ancient Domains Environment. It's the package that Adom 2, which is currently in pre-release testing, runs in. Java as in the computer thingie.
SAGE, I don't think is an acronym and actually I meant JADE when I wrote it, its just I was opening Sage at the time. However, its a third party program that allows various cheats in Adom alnog with management of some stuff thats a bit tricky in game.
ToEF is the Tower of Elemental Fire, a location in Adom.www.adom.de
I can't recommend it highly enough, although the learning curve can be a little steep.