As the name says, you are alone against everyone else. You have to gain XP by building a large base, killing other players or destroying their towers, just like in Teams. To win, you need to control 80% of the map or more, which will stop your enemies from spawning. After that, you have to kill every remaining player without having the territory percentage fall below 80. If you die, you will keep half your XP (when respawning), but not your territory.
You will gain a coin for every 100 points, even if you lose the points.