Might be some tutorials in the flash tutorial thread. (Quick example J.I.C) Like you cant count from 1 to 10 without 2,3,4,5,6,7,8,9.. So in between framing is, if frame #1 has a stick man standing, and frame #10 has the stick man kicking, then frames 2,3,4,5,6,7,8,9 are your in between frames actions going into the kick. So you have to animate each movement til you get to the kick. Some people can skip frames but I like doing each step.
Here's a quick kick with 10 counts. Sorry if it sucks i rushed it but I hope it gets the point across
http://www.filz.us/view/58174777-7ed/