Borrow is what you do when you use (with permission) something that does not belong to you – with the understanding that you will return it.
People borrow money from the bank to buy things like cars or houses. This money (a loan) has to be paid back with interest. The opposite of ‘borrow’ is ‘lend’.
Here are some examples:
“Can I borrow your phone, mine has no battery”. – “Sure, no problem, just don’t be too long, I’m expecting a call.”
“The Greek government borrowed more money than it can afford to pay back and is struggling to pay just he interest on the loans.”
“Can you lend me your blue sweater?” – “No I’m fed up with you always borrowing things – buy your own clothes.”