Normally video's that you see on youtube and other video sites made by video gamers that featuring one or more games or codes, featuring music that isn't from that game/games.
Many people, when making CMVs with cartoon shows, call them AMVs, even though they are using cartoons and not anime.
CMVs are videos in which the creator has different clips, and a song to go along with them.
2: "Whoa, how did you make it?"
1: "It's easy, dipwad. I just get clips and get music and then this masterpiece happens."