Read the following text about Josephine Cochrane and the dishwasher and answer the questions.

Josephine Cochrane devised, in 1886, what it is considered to be the first mechanical dishwasher. Unlike Cochrane's dishwasher, current dishwashers use pumps to create a constant flow of pressure water inside.

1- Explain the functioning of a pump and the concepts of nominal pressure and flow that we can find in a dishwasher pump.