Well, technically everything they do are twists, but a twist can be just about anything. All those suggested options on pages 244-245 are twists, and could either be employed as part of an environment writeup or when a player (or rarely, NPC) triggers a twist - and to confuse things further, the GM can pick an environment twist to go off from a PC doing something if it seems right. It might be easiest to look at as environment writeup as a menu of suggested twists that might happen in a scene, with at least one happening each round as the scene tracker ticks onward. Minor twists can be repeated if you like, majors (by definition) only happen once at most, and might not happen at all if you don’t think they fit.
All that said, fjur provided a bunch of nice examples of environments right here on the forum and if you go over to my blog index here and scroll allllll the way down you’ll find another nine samples to look at. Fjur’s is probably a better learning tool, he’s better about following the guidelines in the rulebook (pages 240-247) than I am - mine cheat more often and tend to be a bit harder than they should be sometimes.