I was a bit surprised to discover the whole jelly-jello language thing. I’d always assumed when people spoke of nailing jelly to a wall that they were talking about something jam-like, not jello-like. I’ve not done the experiments, but I would assume attempting the former would be much less successful.
They also got it wrong in their explanation. To Americans, jelly is jam with the fruit bits filtered out, leading to a homogeneous spread. Jam has crushed fruit, giving it a thicker, uneven texture, and preserves are whole-ass pieces of fruit boiled down in syrup. Marmalade is jam with citrus rinds. As listed here, they are sorted in descending desirability for inclusion in a peanut butter and jelly sandwich.