Conquest is an alternate game mode played on large maps with large ammounts of players. It essentially utilizes the default game mechanic included in WW1:S, only on a more organized scale.
Conquest is organized pubbing. Each team has an overall commander, who in turn appoints squad leaders, who then carry out attacks across the map, with the leader directing them.
All rules for conquest are usually the same, except you can respawn and there are no midlines.
Conquest usually lasts much longer than realisms, and involve a great deal more work.
Tips for this gamemode are just listen to your commanders, and don't bother admins by saying "Change map", they've got enough on their hands already.