What is the difference between being an "entertainer/performer" and an "artist"?

A performing artist does not create but interprates the creations of others such as plays, songs, and film scripts. A creative artist writes the songs, plays or movie scripts. Then there is the singer songwriter who does both or the composer conductor who does both. A comedian who writes their own jokes does both but a comedian who has joke writers performs.

Those are entirely arbitrary designations.

Usually none at all because the people using the word “artist” mean “artiste” - an entertainer or performer.

 “Artist” means a painter or sculptor - a person creating works of art.

Obviously, the word “artist” can be used metaphorically to describe a person doing something in a careful, skilful, artistic way - like a con-artist.

Some entertainers are just clowns, not artists.

It's a huge difference.