I've seen them before used as borrow and lend. So I've been a bit confused on when to use which verb? What's the difference? Is there a difference?
Although the English verbs can admittedly be confusing, you are correct that they are "borrow" and "lend" respectively.
So in the case of borrowing an item,
借りる (borrow) is the verb describing the temporary receiving of the item, and
貸す (lend) describes the temporary giving.
When asking to borrow something either of these are acceptable:
借りてもいいですか？ (Can I borrow it?)
貸してもらえますか？ (Will you lend it to me?)