Just the basics (these are in general):

What defines them are whether or not the string touches the back of the limb while the bow is at brace. Longbow does not touch and recurve does. Selfbows are like longbows but are made from one piece of wood.

Longbows are usually quieter, weigh less, have narrower limbs, have a bit more hand shock.
Recurves are usually faster, more stable, heavier, cut to center, and louder.

Grips are also usually a bit different between the two. In general, the longbow is shot with a low grip and the recurve with a high.