Engine/Tile pack

1

Just to clarify, I have made some games already so i wont be coming to you guys for much more help. All i want is for some one to explain game engines to me. Also my game will be a tile-based RPG. I have read a tutorial about creating a 100 tile or so tile pack for different areas in my game, and the game would recognize that it needs a certain pack for a specific map. Even if you could just tell me what some things i should read up are, that would help