Monster Warlord is mainly about fighting. Using your monsters to fight for you. These page should provide you with enough information on this matter:
Battles - information about types of battles in Monster Warlord
Boss Battle - more information about Boss battles and Bosses
Arena - more information about Arenas
Team Battle - more information about Team Battles
Dungeon - more information about Dungeons and its bosses and rewards
World Boss - more information about World Bosses
World Boss Rewards - regular World Boss rewards in a list
If this is not enough, then try using search bar in order to find more useful information.