DPS stands for damage per second. This means how much damage a unit can inflict in a damage to time ratio (seconds).
Lets say we have a robot named "Pillock". Now, Pillock does 720 damage every 60 seconds with his decoder ring.
720 Damage / 60 seconds (60 seconds in a min.)
Thus, Pillock has a total DPS of 12 damage.
If a unit has guns that shoot for 100 damage per shell, and fires 3 shells every 2 seconds, it does 150 DPS [(3x100) damage / 2 seconds]