A nice short piece here by Mike Rowe of Dirty Jobs explaining the difference between Jelly and Jam.

I couldn’t believe it when I first read it either.
“I guess Im like the guy whos never seen Star Wars. But I never thought it was a huge deal to have never eaten a peanut-butter-and-jelly sandwich. My mother just never pushed it. She says I told her I didnt want it after I watched a kid in third grade ball one up and fling it across the room…”
Read more here.
How do you like your PB&J?

As we all know, the truth is very hard to come by. I guess it’s down to me to tell you the real truth. In a recent post, Edward described to everyone what he thought jelly and jam were. In reality, all of it was false.
Jelly and jam are actually the same thing. The only difference between the two is jelly goes well with peanut butter. Howcan you be sure this is true? Well, nobodyhas ever made a peanut butter and jam sandwich; that’s for sure. We all know peanut butter goes with jelly, not jam.
Take a look at the photo above. Same packaging, same contents, different flavor. If that’s not solid evidence to prove something, I don’t know what is.
Jam. It’s sticky, sweet and fruity - goes well with toast. I don’t rank it highly among foodstuffs, but I prefer it over marmalade when spread on hot bread slices.
Jelly makes a fruity dessert. Non-fruity jelly also exists, like the jelly inside pork pies (which are usually more pie than pork). Jelly is not good on toast.
Not a very comprehensive review, but it should be enough to confirm your suspicions and help you identify one from the other.