The Track View hierarchy, as displayed in the Controller window, follows the traditional example of organizational headings in an outline. The highest levels of the hierarchy represent the main groupings in 3ds Max of Sound, Environment, Materials, Render Effects, and Objects. Lower levels of the hierarchy progress through the details of your scene, such as individual materials, material maps, and map parameters.
Each type of item in the Track View Hierarchy List is represented by an icon. You can use these icons to quickly identify what each item represents.
Indicates material definitions. All branches below a material definition are part of that material. Because a material can be composed of multiple materials it is possible to have nested material definitions in Track View. Icons also appear in an object's modifier branch when a material is assigned to an object.
Indicate an animation controller, which contains the animated values for all parameters and is the only item type in the Hierarchy list that can have a track containing keys. Every controller has its own individual icon. Some examples:
Certain types of controllers can contain other controllers. Examples of these are Transform controllers and List controllers.