Track View > Select a track in the Track View hierarchy. > Track View menu bar > Controller menu > Assign > Choose a controller in the dialog.

Animation menu > Constraints/Transform Controllers/Position Controllers/Rotation Controllers/Scale Controllers> Choose a controller.

Select an object. > Motion panel > Assign Controller rollout > Select a track. > Assign Controller > Choose a controller in the dialog.

Controllers, like constraints, handle the animation tasks in a scene, including:

An object or parameter doesn't receive a controller until you animate it. As soon as you change an animatable parameter with Auto Key on, or add a key in Track View - Dope Sheet, the software assigns a controller to the parameter. The software chooses a default type for the controller, depending on the animation. You can change the default controller to another type.

The animation controllers are organized in the following categories:

To change an assigned controller, use Controller > Assign in Track View or in the Motion panel.

The controllers and constraints are:

Attachment Constraint

Audio Controller

Bezier Controllers

Block Controller

Boolean Controller

Color RGB Controller (Point3 XYZ Controller)

Euler XYZ Rotation Controller

Inverse Kinematics (IK)

Limit Controller

Linear Controller

List Controller

Link Constraint

LookAt Constraint

Noise Controller

On/Off Controller

Orientation Constraint

Path Constraint

Position Constraint

Position XYZ Controller

PRS Controller

Scale XYZ Controller

Script Controller

Slave Parameters Dialog (Block Controller)

Smooth Rotation Controller

Surface Constraint

TCB Controllers

Transform Script Controller

Waveform Controller