A marriage certificate usually contains who married who, when they were married, where they were married, who married them, and who was there.
It is generally the responsibility of the officiant of your wedding ceremony to make sure that your signed marriage license is delivered to the recorder's office. Since the recorder's office has to process the filing and recording of the marriage license, you usually have to wait several weeks before receiving your marriage certificate.
In some locales, once a marriage license is signed and filed with the county clerk, the license becomes the marriage certificate. Generally, in order to receive an additional copy of a marriage certificate, you need to send your request along with the required fee to the County Clerk/Recorder's Office of the county where the marriage took place.
In order to be acceptable as a legal document, a Certified Marriage Certificate needs to show the state seal or be imprinted with a seal/stamp. Keepsake marriage certificates are not legal documents.