If a check is issued to two people, such as John and Jane Doe, the bank generally can require that the check be signed by both payees before it can be cashed or deposited.
If a check is issued to John or Jane Doe, generally only one payee needs to sign the check.
If a check is unclear as to whether it is payable to both payees or just one payee—such as if it is payable to John and/or Jane Doe—you should ask your bank what the guidelines are.