Most loans have a grace period before you have to start repaying. Your grace period starts the day after you leave school, graduate or drop below half-time enrollment. You don't have to begin making payments until your grace period ends. Perkins Loan borrowers have a 9-month grace period and Direct Subsidized and Unsubsidized Loans have a 6-month grace period. PLUS Loans do not have a grace period.
You will not be charged interest on Stafford Subsidized Loans while you are in school or during your grace period. Unsubsidized Stafford and Graduate PLUS Loans are charged interest while you are in school and during your grace period. You may choose to allow the interest to accrue and be capitalized (added to the principal of the loan). Having your interest capitalized is a more expensive option than monthly payments while you are in school.
If you borrowed loans from a private lender (not from the government), then you will need to check with that lender for the terms of repayment. Private loans are separate from government loans and have different rules about repayment.