The pump works by constantly dripping tiny doses of rapid insulin into your body. That is you basal which acts like a long acting insulin, instead of 1-2 shots of slow releasing insulin you get a constant drip. Then you can adjust how much more you will need during certain times of the day. When you eat, you will need to enter the amount of carbs into the pump and the pump will figure out how much insulin to give you, depending on your carb:insulin ratio. There are many other features of a pump, and every pump is a little different. Some are more automated.