The verb license or grant license means to give permission. The noun license (licence in British spelling) refers to that permission as well as to the document memorializing that permission. License may be granted by a party ("licensor") to another party ("licensee") as an element of an agreement between those parties. A shorthand definition of a license is "a promise (by the licensor) not to sue (the licensee)."
A certificate may also certify that a person has received specific education or has passed a test, and is considered below the standard of an academic degree.