Just to be clear (once again for the umpteenth time), I am not a creator.
Just by searching "commission writing" (why can't you do this yourself?), it clearly says what this all means.
Basically writers, like artists, are selling their talents to people who want certain stories to read.
However, not everything they work on is for commission. For example, artist Jeff Lemire may work on an Animal Man print for someone as commission, but he will also work on his creator owned works like Black Hammer or Gideon Falls.
I did not think I had to explain this all to an animator who wants to make his own work, as he has repeatedly said.
At this point, I can probably start making a 4 panel web comic using all of the information I gathered for you these past years.