Credentials offer proof of a fact, or of qualifications. A driver’s license, a doctor’s badge, or a diploma all count as credentials — as long as they’re real!
One document can be a credential, but the word usually still gets pluralized. Credentials prove that the bearer has gotten credit for what he or she has done, as with a transcript, diploma, or certificate proving a person’s activities. Your credentials allow you to get the job, but your skills are what make you good at your job. Credentials can also prove that you are allowed to do something or go somewhere, like a badge that gets you past security.