Basically...
The pump user has to programme the pump to give insulin.
This is initially done with your diabetic nurse, but after a while the pump user must be prepared to programme the pump themselves.
The pump delivers insulin constantly according to the data in it.
When you eat you have to tell the pump how many carbohydrates you are eating... And again according to the data that is programmed in to the pump, the pump will push the insulin into you instead of having to give a fast acting bolus injection.
You have a very small either steel or plastic needle in you, connected to the pump which you will have to change every 2-3 days.
You do not feel the constant background insulin going in you or the bolus's.
It is a lot nicer than injecting, but initially more blood tests and learning to get the pump set up right.