There is quite a bit of confusion surrounding marriage licenses and marriage certificates. People often conflate the two even though there are important differences between the two.
Marriage licenses are the government issued legal document of marriage. A real marriage license can only be issued by a government office. This is the document that needs to be completed on the wedding day and returned to its issuance office.
Marriage certificates are commemorative mementos of the wedding that are intended for framing or otherwise displaying. Marriage certificates are not legal documents. They can be sold by anyone and are solely intended to commemorate the wedding day. Couples often sign these documents alongside their marriage licenses after the wedding so that they have something to remember the day (the license must be filed with the local government office, and is not commemorative).
For instance, we sell marriage certificates however these are not legal documents. Instead, they are crafted documents that we issue so that the couple and witnesses can sign something for pictures and memories. The couple is required to file for a marriage license in order to be legally married. They are not required to file for a marriage license.