APR is the total yearly cost of borrowing money, including the interest rate and most fees. It gives you a complete picture of a loan's cost, making it easier to compare financing options.
APR is not just the interest rate. While the interest rate is the cost of borrowing the principal, APR adds in other charges like origination or closing fees. This is why APR is usually higher than the stated interest rate.
Lenders are required to disclose the APR so you can make informed decisions.