The SotDL world.

Book names (of Shadow of the Demon Lord)

SotDL, Core
Shadow of the Demon Lord, core book; also to refer to the system and the setting. Sometimes written as Core to leave SotDL as a term for the setting or system.
Shadow of the Demon Lord: Player’s Guide, subset of the core book that includes most of the non-GM
Victims of the Demon Lord: Starter Guide, a PWYW (free) quick-start, with a smaller subset from the core book thank the Player’s Guide. With the exception of spell lists, everything you need to play. No reason not to get it. Go get it. Now!
Demon Lord’s Companion, (no, not the things that complete computer games, but the thing that completes SodDL). SotDL (the core book, I mean) was pretty big and Rob Schwalb, the author to extract some part of it to not make it a humongous core book. I consider it for most intents and purposes part of the core too.

Standard RPG or whatever

Role-Playing game
Tabletop RPG; basically it exists to contrast with computer RPGs (or LARPs too?)
Game Master (or many other names)
Pay What You Want