Similar to SOCOM, it's team deathmatch but with a twist. When you die, you don't respawn. Instead, you go into a "downed" position. If a teammate goes next to you, they can "revive" you clicking+holding your body until a bar fills up. Then the person is back in the game. When everyone from one team is in the "downed" position, that team loses.
2:30-2:40 shows exactly what I mean.