Replay Mode

When playing an animation channel on the entity's skeleton, there are two modes: the Rest Relative Mode and the Absolute Mode. If the skeletons are similar, both will play the motion in the same way. But results will be different when the skeletons are different, like for instance a difference in the arm's orientation at rest:

Slightly different arm's orientation on the entity's skeleton and the animation's skeleton

Playing the arm's animation from the right skeleton can mean two different things:

either it's important to keep the base skeleton's orientation, and just add the animation on top of it (rest relative mode);
or it's more important to keep the absolute orientation of the arm in the animation whatever the base orientation was (absolute mode).

*

Replaying the same motion with different replay modes on arms:

rest relative mode on the blue character
absolute mode on the green character*

Note:

In most cases, the Replay Mode should be configured

in Absolute Mode for all extensions for any kind of limbs except for the head
in Rest Relative mode for all auxiliary for any kind of limbs, and also for the head's extension