Knowing whether or not a step is a leap or a jump helps you know where to put your energy. Do you go up in the air, or travel across the floor? Where is your focus? And how does changing that energy affect the combination/choreography?

A leap is any step that moves through the air and goes from one foot to the other. Your focus is movement across the floor.

Grand jeté: you brush one foot up into the air, and leap onto it.
Petit jeté: you’re brushing one leg and landing on it (though in coupe).
Glissade: you brush one foot, leap onto it, and then close the other one.

Jumps are a little different. They usually don’t travel (or they travel only a little) and the focus is getting up in the air.

Sissones jump up into the air and land on one foot.
sauté jumps up and lands, and doesn’t travel at all.
Temps levé jumps up and down on one foot only.
Assamblé under jumps up off of one foot and lands on two feet.

But there’s one that doesn’t fit.. Assamblé. (It's special, it gets it's own post.)