Loans do have to be paid back. Useful but not the best (see the previous line).
Like any other loan for a house or a car, banks charge a fee (called interest) which is a percentage of what you borrow. In fact, they charge interest continually and interest then begins to be charged on interest. In other words, depending on how quickly you can pay back the loan, you will pay extra beyond what you borrowed (called principal).
Some educational loans start charging interest right away--not the best.
Some wait until the year after you graduate--a lot better .