Motion tweening was introduced into flash as an alternative to more traditional methods such as keyframe animation, which was outlawed because of its limits and boundaries. Tweening for flash covered leaps and bounds because it allowed the user to use flash as an automation. When one would tween, flash would, in a sense, guess, or calculate the best position or appearance for each frame that the tween covered. This allows the user full control over what the tween's actions and appearances are without the mess and wasted time.
1. The first thing you want to do is make some text. It can be any text you prefer. The idea, though, is to place it on the left side of the canvas. You will understand why later in the tutorial. =)
2. The next thing you should do is insert a keyframe in frame 20 like the image on the left. Then, with the frame selected, drag the text you created over to the right side of the canvas.
3. Then, select frame 10 and right click. From there you should see a menu popup with different commands and properties for that frame. You will want to choose "Create Motion Tween".
4. This should be the final result. If you want to view your animation quickly and easily, you just hit ctrl+enter.
More Flash & Swish: 
