"Accredited" means that something has received credit for something. "Credit" is a noun for some sort of representation of accomplishment. For example, if you went to a university that wasn't accredited, the credit that you received from that university wouldn't be worth anything. Or, if you were to share someone's art with some friends, you should accredit the artist for making the work, instead of claiming the artwork was yours.

Credit is a noun, which means honor given through your actions. Example: "He deserves credit for the hard work he put into his project." Accredited is an ADJECTIVE, meaning you are recognized for your actions. Example: "He is an accredited scholar."