When you LEND someone money, you LOSE money because you LET someone have your money (with the expectation that they will pay you back the money).
When you BORROW money, you get BIG BUCKS from someone (with the expectation that you will pay them back).
Examples: I don’t have any money. Can I borrow $5? / No. Every time I lend you money, you never pay me back!
Important Note: You can lend and borrow other things, not just money.