The word hammer has two main meanings:

1. A tool with a heavy metal head attached to a handle, used for driving nails into wood or breaking things apart. When you hammer a nail, you swing the tool so its metal head strikes the nail repeatedly, forcing it down into the wood. Carpenters, builders, and sculptors all rely on hammers. Different hammers serve different purposes: a claw hammer pulls nails back out, a sledgehammer breaks through concrete, and a ball-peen hammer shapes metal.
2. To hit something repeatedly and forcefully. Rain might hammer against your window during a storm. A teacher might hammer home an important point by repeating it several times, making sure every student understands. When you hammer away at a difficult problem, you keep working at it persistently. A basketball team might hammer their opponent, winning by a huge margin.

The word captures the idea of repeated, forceful impact. Whether you're using an actual hammer to build a treehouse or hammering out the details of a group project with your classmates, you're applying steady, determined effort to get something done.