This is your character's ability to concentrate on mentally involved tasks for periods of time. It is used up when employing skills such as Mecha Engineering, First Aid or Robotics. Your max Mental Points is (Ego + Knowledge + 5)/2 + 3*Concentration.
You regain about 1/30th of your Mental Points every ten in game minutes. Mental Points can go negative. They will display as 0 while negative but they will still take the full amount of time to regain.