The name and description sums most of it up.
What I want to know is how to show motion, using graphite pencils as a medium. In cartooning, there are action lines, and with paint, I think you sort of lightly put some more paint to the direction which it is coming from, so it looks stretched funny.
But what I want to know is how to do a natural drawing with graphite pencil, of an arm moving to the right, a tiger leaping, etc.
Any help?

I remember Rolf Harris saying once that to show movement or differences between heavy and light, the more you got to work with the easier it is. I.e. A female tennis player reaching for a backhand would show the direction of her body, which muscles are being put under strain and also not forgetting the position of her skirt which would be held down if she was jumping up but would be billowing a little if she was on her way back down.

Don’t know if this helped any, but there are far more experienced people here at DrawSpace that can help

no, that does help, thanks

Lance's point is correct. Positioning of the body or clothing is what shows movement or potential movement.

I haven't seen much in the way of depicting movement besides a drawing that depicts what the eye knows is movement, but it would be a single still image.

You could blur the external lines of the drawing or perhaps have a series of ghost images moving in the expected direction. These would be faint outllines attached at the same point to the original figure, in a series of incremental movements til you get to the final point.

Jeanette just reminded me of an artist called Nick Archer, he paints some of his subjects in a sort of a blur to give them the feel of motion

http://www.archerart.fsnet.co.uk/portrait_frame.htm