Team Deathmatch: 100 players on 2 teams. Team with highest score at times-up wins
Skirmish: 6v6. Hold flags until victory or reduce enemies to 0. Gain gold on kill, respawn by buying a unit of a certain class. (knights cost more than peasents). When you can't afford anything then you are out for the round
Captain mode: 6v6. Teams start as random factions. Each player picks a squad of units (infantry, archers, calavlry). Either destroy all enemies, or win by holding the majority of flags for a time. 3 flags, 2 disappear after a few minutes.
Captain is my favorite, TDM is alright for practice fighting, skirmish is kinda boring to be honest.