Motion

When an imported animation clipAnimation data that can be used for animated characters or simple animations. It is a simple “unit” piece of motion, such as (one specific instance of) “Idle”, “Walk” or “Run”. More info
See in Glossary contains root motionMotion of character’s root node, whether it’s controlled by the animation itself or externally. More info
See in Glossary, Unity uses that motion to drive the movement and rotation of the GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary that is playing the animation. Sometimes however it may be necessary to manually select a different specific node within the hierarchy of your animation file to act as the root motion node.

The Motion field within the Animation import settings allows you to use a hierarchical popup menu to select any node (Transform) within the hierarchy of the imported animation and use it as the root motion source. That object’s animated position and rotation drive the animated position and rotation of the GameObject playing back the animation.

To select a root motion node for an animation, expand the Motion section to reveal the Root Motion Node menu. When you open the menu, any objects that are in the root of the imported file’s hierarchy appear, including None and Root TransformThe Transform at the top of a hierarchy of Transforms. In a Prefab, the Root Transform is the topmost Transform in the Prefab. In an animated humanoid character, the Root Transform is a projection on the Y plane of the Body Transform and is computed at run time. At every frame, a change in the Root Transform is computed, and then this is applied to the GameObject to make it move. More info
See in Glossary. This may be your character’s meshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
See in Glossary objects, as well as its root bone name, and a submenu for each item that has child objects. Each submenu also contains the child object(s) itself, and further sub-menus if / those / objects have child objects.

Once you select the Root motion node, the object’s animation drives its motion.