Jam- whole fruit used in making it.
Jelly- just the juice of the fruit is used in making it.
I just realized I didn't actually post, but this, with the result of the second option.
I'd completely forgotten that jelly was the normal non-American term for jello, as ubiquitous as that trademark has become here. The generic term for jello here is 'gelatinous pudding,' which sounds just so
appetizing no one can bear to use it, so jello it is. Presumably 'jelly' never got a chance at it because it already meant the preserve.
It never actually occurred to me that anyone would normally say 'preserve,' though. It has the sort of technical connotation here that words like 'watercraft' do, and so is only used in cases such as I have here, to group jams, jellies, and marmalades together.