Whats the difference between a cordless drill and a cordless hammer drill?

I want to buy my husband a cordless drill. Ive been looking at the Dewalt brand and they have a cordless drill and a cordless hammer drill. Well I found out he wants to switch to Milwaukee and ive been looking around and all I see for that brand is a hammer drill. So whats the difference?
Update: My husband farms so I would never know for sure what he would be using it for. I know he always wants the "best" he firmly belives that you get what you pay for and the more you pay the better your getting. But the one he has now is not a hammer drill and i dont recall him ever saying that he wishes he... show more My husband farms so I would never know for sure what he would be using it for. I know he always wants the "best" he firmly belives that you get what you pay for and the more you pay the better your getting. But the one he has now is not a hammer drill and i dont recall him ever saying that he wishes he had a hammer drill.....
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