If, for some reason, your newborn doesn't come home with you you may be asked to express your milk so Baby will have the benefit of being breastfed while you are not there. This has two benefits. One, Baby gets the very best nutrition possible and it keeps your milk flowing while you cannot hold your baby and nurse together. Breast milk is very much a 'use it or lose it' proposition. If it is not used, either by nursing or expression it will go away very rapidly and you will not be able to bring it back.

Manual or electric?

Generally speaking breast pumps are one of two basic types, manual and electric. There is a huge variation of style and price in each of these types but they all do basically the same thing, extract breast milk through a sucking motion produced by a vacuum. They are meant to imitate a baby nursing but since very few human babies nurse like a shark in a feeding frenzy many of them fall short in this area. This is probably because most of them are designed by men. Men sometimes have breast if they are overweight but they never lactate. Clearly there is a conflict of interest.

Electric pumps are very efficient. They are also very expensive and probably weigh more than your baby. Renting one may be a better option than buying one as, hopefully, you will not be needing it for very long.