Jelly is made from fruit juice and is clear with no solids in it.
Jam contains the whole fruit and it chunky or lumpy and opaque.
I think there are preseves, conserves and marmalades which are
some combination of the above. my favorite is hot pepper jelly!
pectin can be found in apple esp skins, and seedparts. some
fruits require added pectin to "jell" others "set-up" on their
own. one brand is called sure-gel. i have been known to use agar-agar
to thicken som fruit spreads--from sea weed.
and some like apple butter are thickened by cooking off the liquid.