I'm asked all the time what's the difference between a jam and a jelly.  Fair question. 

If you had a spectrum of spread based on their thickness:

1.  Jelly would be at one end.  It is made with only juice. 

2.  Marmalade is the next thickest spread.  It is basically a jelly in which citrus rind or small pieces of fruit are suspended.  Think of grapefruit marmalade, orange marmalade, etc.

3. Curds are creamy spreads made from juice and butter.  I love, love, love lemon curd.  I use it as a filling for cakes.

4.  Butter is the next thickest.  It is pureed fruit.  Think pumpkin butter.

5.  Next comes a jam.  Jams are made of crushed fruit.

6.  Following a jam is a preserve.  Preserves are made from chunks or slices of fruit.  After cooking a preserve, it may retain some chunkiness, or the fruit may cook down to a smoother spread, much like a jam. 

7. Finally, you have a conserve.  This spread must contain a citrus, a nut or raisin (or both), and at least one other fruit.  This spread is definately chunky.

There are other varieties of spread that folks in other countries might add to this list, but this is pretty complete for the U.S.