Just because you graduate Law School doesn’t mean you can practice law. You still need to “pass the bar”, or specialized legal exam. In much the same way an attorney needs to do more than simply graduate law school, many professions require a credential to show competency for their particular vocation.
What’s the difference between a credential and a certificate?
Credentials are awarded following an advanced level examination delivered through a third-party testing service (passing the state bar exam for an attorney). In contrast, certificates are awarded for completion of an educational program (similar to receiving a Juris Doctor diploma from a law school).
Here are the links to some of the most commonly required credentials by industry.