A debit card gives you access to the funds in your bank account. Policies vary by bank as to when you can open an account and get a card. You normally have open access at age 18, the age of majority in most states. Some banks allow minors access to a debit card when they open a join checking account with parents.
A joint account means you share benefits and responsibilities of the account with other owners. A parent often can open a joint account with a minor at the bank. Some banks limit joint accounts with minors to those ages 14 and older. With a joint bank account, both account holders get a debit card. Each can use the card at automatic teller machines to withdraw cash, or at store registers to pay for items.
An alternative to a joint checking account is a student checking account. Banks may offer these accounts to minors around age 16. While parents still have to sign as joint account owners for students under 18, this type of account is tailored specifically to the needs of high school and college students. You get a debit card and have the same basic privileges in using it as you do with a joint account. Student accounts often have few, if any, maintenance and debit card usage fees.