WSG starts at level 10, bracket is 10-19, etc.
This graphic shows the two bases: Alliance (left) and Horde (right).
Warsong Gulch is a battleground hosting a capture the flag style match with 10 on 10 action.
The loading screen for WSG.
Capture requires that both flags be in the same flag spot at the same time. If your flag is out on the field, you cannot complete a capture of the opponent’s flag. When you kill the flag carrier, it causes the flag to drop on the ground and either the opposing side can pick it back up and continue on its way with it, or the team whose flag it is, can return it to the base. Whoever captures the flag 3 times first is the winner.
Here is some PVP action taking place inside the Alliance base in Warsong Gulch.