These are needed to play most Interactive Fiction Text Games.
TADS is one of the three most popular text adventure development platforms. Two basic types are text-only TADS interpreters and multimedia TADS interpreters.
The Z-Machine is the format used by Infocom, and now compiled to by Inform, one of the three most popular platforms for development. You can get an interpreter for practically any system out there, and source is usually available. Please do not ask anyone for Infocom games to play with these interpreters, as these are still under copyright in the majority of the world.