feat is short for Featuring, which means that the singer (or group) behind him is not the protagonist in this single or this album, but the person in front is the soul or owner of this song.

feat. is the abbreviation of feat. Featuring can be understood as deduction, such as A featuring B, which means that singer A and singer B*** perform the same songs, while A is the protagonist and B is the backup singer or their forms of cooperation. The most common thing is to insert a RAP or sing it in a song.

Extended materials:

1. "feat" means "cooperation and chorus". Or understood as: two or more people sing a chorus that is relatively minor to the lead singer.

2. Featuring is very common, mainly those who play hip-hop and rap, and basically pull one or even several people to play a song together. Generally, the names at the back are singing harmony or rapping and so on.

Reference: Baidu Encyclopedia -feat