Animations in Total war controls a great deal, but its important to know that the game has no idea what an animation is. It depends on configuration and meta data to actually use it for anything apart from a visual display.
The game often works by stacking animations on top of each other. Such as walk + attack + close hands = moving attack.
Most animations can be view in AssetEditor or RME. The animation files can be edited in RPFM, and viewed (soon-ish edited) using AssetEditor
The animation pack is the main file which acts like the container of the bin file and the fragments. This file can be edited using RPFM. To do so you must unpack the files inside of it and make sure that you repack them when done.
The bin file contains the key that is used by the database and links that with a skeleton, and optional mount bin entry and a set of fragments. Most entries contains multiple fragments, where the fragments later in the list overrides Slots in earlier fragments.
The fragment files contains the actual capabilities of the animation set. This is where you link action with the visual animation.
The "Slot and Id" tells the game what action the animation should trigger for. If you try to use any capabilities without having the slot, it will often not work. For example adding a ranged attack without adding the correct Slots will result in the unit not being able to fire its weapon.
For each row there is also a meta file which can override how the animation looks, as well as add effects such as particles, camera shake, hit position, AOE, etc.
The row also contains a checkbox for which prop slots in the VMD should be visible.
Animation meta (.meta.anim)
The game uses two different mount systems:
Attachment point mounts
The attachment system is used for two different things; Rider animations for units not really doing much (unit on top of a war mammoth which is just sitting there, no matter what is happening) and units with multiple riders which are attacking but not moving (Necrofex, war-wagon)
Attachment point mounts riders are officers
Synced animation mounts
The most common mount system is the one for synced animations. Both the rider and the mount must have the same slots. (Typically Attack_1 and Rider_attack_1) where both animations are synced to each other.