CAT uses a layer-based animation system, which means that all keyframes are created in layers. There are two types of layers for keyframe animation: Absolute and Adjustment (relative).

Absolute layers are used to create new animation. Standard animation controllers store all transforms in the same way as when you animate other objects.

Adjustment layers are used to tweak existing animation. Keyframes in an adjustment layer offset existing layers below them in the stack, including CATMotion.

Keyframe animation in CAT is as simple as selecting the element you wish to animate and transforming it in the viewport. A CATRig is set up so that you can just push it around into the pose you require.

Because your animation is stored in standard 3ds Max animation controllers you can create and edit your animation as you are used to. Keyframes can be edited in Track View as normal.

How various rig elements and sub-elements relate to each other is dictated by their setup parameters, accessed in the Modify panel. Some rig elements have extra animation parameters too; most notably the limbs, palms, and ankles.