It's this thing with a point at the end attached to a chain - if you press a button on the handle, it shoots out, and if you stick it in something like a target or wood or something, you can press the button again and the chain retracts and it pulls you over there. Or you can use it to bring stuff over, or you can use it on some enemies - like those bubble things. On bigger things, it just stuns them, though.

[You know that little window thing? It's now showing Link holding up the hookshot - well. Technically, the longshot, but close enough.]