Motion tweening

Watch this tutorial on classic tween. https://www.youtube.com/watch?v=tjE__KwrTIQ

What Nick said.
Motion tweens are OBJECT based
Classic tweens are FRAME based
The difference is, with Motion tweens, you can set what the starting frame is but it's global across the tween. If you insert additional keyframes and try to change the nested frame nu mber, it will be applied across the tween span.

With Classic tweens, you can insert as many keyframes as you wish and edit the viewable nested frame however you like. You also have the option to sync or unsync nested animations across keyframes within a Classic tween span.

This is why animators who rely on their motions to be in sync across multiple timeline only use Classic tweens and Graphic symbols. Many years ago Adobe implemnented the Motion tween to replace the original tween modfel and it broke our workflows completely. We asked for that ability to control nested frames and they decided to bring back the original tween model alongside the newer Motion tween model and call it "Classic tween".

It's very con fusing for anyone new to Animate and it's tricky to even explain the difference via text-based forums. But know this: Graphic Symbols + Classic Tweens = happy animators

Only use Classic Tweens and make sure your body part elements are all symbols.