When an employee is certified, they receive proof that they have the knowledge or skill required. The requirement may come from an authority, a customer, or the company itself.
A certificate should stand on its own. It should show who it was issued to, what it covers, when it was issued, and whether it expires.
In a learning platform, the certificate can be the last page of a course. It is then issued automatically when the employee completes the course, and the company has the documentation gathered in one place.