When you lend something, you loan it or let someone borrow it. You might, for example, lend your bike to your brother — if he promises to be careful with it.
Libraries lend people books, and car rental companies lend people cars — in both cases, the item that's been borrowed is supposed to be returned eventually. Another way to lend is to "add a quality to," or "be suitable for." You could say that you think your hat lends you a mysterious quality, or that your trench coat lends itself to walking through a foggy city at dusk.