Sync License or "Synchronization" refers to the use of music in movies, television shows, advertisements, video games, presentations, YouTube videos or any other product where music and moving images are used simultaneously.
When a song is licensed for synchronization, the composer / publisher receives a fee for the use of the underlying composition, and also the owner of the rights to the original recording.
If you have written a song and you have not sold the rights, you are the publisher. If you are the owner of the recording, you are the rights holder. In this case you will receive both fees.