Stupid question. Ive never had a credit card

Basically ive never had a credit card. Im 20 now. I was looking into the chase freedom unlimited. But i always heard basically you can use credit cards even though you have no money in it as its borrowing from the credit card company. Basically using money you don't have, is this true? I was only wondering cuz i need one in case of an emergency case where i desperately need to pay a bill or something