What are jQuery hooks and callbacks?

I am having a tough time conceptualizing what exactly callbacks or hooks are in jQuery. They seem to be lumped together, but I don't know the difference between them.

From what I understand from other posts about callbacks, like this, a callback is simply a function A that you pass to another function B that calls A once B is done. (That may be totally wrong, correct me if so).

I really don't have any notion on hooks, other than the statement "you should use a hook/callback." Something makes me doubt they're that similar...