Flash 101 (part 3): Bouncing Around - Taking The Scenic Route (Page 5 of 9 )
By default, Flash chooses the shortest distance between the starting and ending positions of the object as the motion path. If this is not to your requirements, you also have the option of tweening motion along a path that you define.
Let's consider a new example to illustrate this better. Open up a new Flash movie, and at frame #1, create a small dot with the Brush tool. Convert it to a graphic symbol.

Next, move to frame #25, insert a new keyframe and move the dot to the other end of the stage.

Create a motion tween and play the clip - your dot will travel horizontally across the Stage, since that's the shortest distance between the two positions.