You start as attacker or defender.
Defenders try to keep attackers from using vehicles to blow trough the gates and reach the inner core where the relic is. Once the gate to the relic is broken one attacker stepping inside is enough for attackers to win.
Gates can be damaged by people carrying seaforium bombs wich seems to be unlocked once attackers capture workshops.
Defenders win the round if time runs out.
After round one you switch side so attackers become defenders and those defending earlier are attacking.
Winner of the bg is the one being quickest at capturing the relic/being only one to capture(can also be a tie if both sides fail to capture it).
Short version:
Winner is the team with the best zerg and its usually a good idea to have people going for the same gate.
