I recently found out theres a distinct difference between jelly and jam. The latter has parts of the fruit mixed with the sugar and whatever gelling agent you use while the former only has the juice of the fruit.
Look at these choice quotes from the wikipedia article:
Peanut butter and jelly sandwich - Wikipedia
en.wikipedia.org
A peanut butter and jelly sandwich (PB&J) consists of peanut butter and fruit preserves—jelly—spread on bread.
There are many variations of the sandwich, starting with the basic peanut butter sandwich or jam sandwich.
If you're using jam then you're having a half jam/peanut butter sandwich. It's not a PB&J.
I also heard word on the street that the default fruit jelly of a PB&J was grape. I never had that either.
I'm just a fool who likes to slap together strawberry jam with peanut butter.
tbh I prefer jam sandwiches with butter more.