Jelly vs. Jam - yes, you both have jam correct - pieces of fruit, maybe and very thick! Oh my, now jelly - no pieces of fruit, thin, almost see thru color if it's like apple or peach, not dark like grape. No gelatin at all. Just the juice of the fruit, sugar and is used and boiled down. Sometimes the skin is thrown in to add a deeper color and then you remove it. I think that's the basic difference, it's been a long time since I made either. OH and we would seal the jars with melted paraffin wax. And then there's pectin ... had to go to Ms. Goggle for exact description - If you’re working with low-pectin or overripe fruit, adding flavorless commercial pectin is one way to achieve a thick texture. “There is absolutely nothing wrong with adding pectin to preserves, especially if you like a more consistent product, We've got Marmalade, Preserves, Jam, Jelly - in order of amount of fruit and the 1st 3 are about even in thickness, jelly is thin. PB & J is usually jelly!