In MAG, as with almost all shooter games, you will (at some point) be killed. When you are killed completely, and are not Bleeding Out, you will be taken to the Respawn page. Here you can do a number of things; choose your respawn location (which can vary as the game progresses) and choose your Loadout for your respawn.
While waiting to respawn, you can see a brief look at the battlefield from the camera position, and the Respawn Clock is also visible. This clock is in place to ensure that the battlefield is not swamped with players respawning at different times. All dead players will respawn at the same time, which is set at 20 seconds, and can be altered by the Highest In Command.