The peanut butter, with it's thicker texture and protein is obviously the meat, and the jelly, with it's more liquidy texture and lack of nutrition is the condiment
Peanut is a versatile flavor. Sweet, savory, whatever.
You could use it with ketchup if you like. The mix could be a pretty nice combo to use as a sauce for a Thai dish, honestly. Just on bread would probably be pretty overwhelming alone.