A "loan" is money that one person lets another person use, which they expect to be paid back.

We use the word "lend" to talk about giving someone a loan:

They might agree to lend you a few thousand dollars.

In American English, we can also use "loan" as a verb:

Can you loan me a few bucks?

Some people feel that "loan" should only be used as a noun ("a loan"), so use "lend" if you're writing or speaking formally.