An alehouse was a place, in the past, where people went to drink ale — a kind of beer. Before the modern pub, many English towns and villages had alehouses. Often it was simply a room in someone's house, with a sign outside; you sat, talked, and drank. You did not usually sleep there — that was more an inn. The word itself feels old. A history book or a story set long ago will use it. A person asking for a drink tonight would say pub, bar, or the local, not alehouse. You may still see it on a cute modern sign, but that is someone playing at the past.