The 'Constraints' panel contains all necessary tools to rig characters, props, animations in After Effects. These are the tools you can use after you have created some Structures, to make them move as you wish, and manipulate them with handy controllers.

• Autorig & IK are (automated) tools mostly used to rig humans and animals.
• The Connector is a way to control almost any property in After Effects with any other property, a bit like parenting between layers.
• The Animation Blender is a tool to animate using markers to trigger animations.
• The Bones are layers used to control spatial properties of effects (including the puppet tool pins, but not only them), or Bézier shapes since After Effects CC2018, allowing to use parenting, expressions and the other rigging tools with them, from Duik or any other script.
• The Parent Link tool replaces the native parenting of After Effects and allows to animate those links.
• Parent Accross Comps is a way to simulate parenting a layer to another one in a parent composition or in a precomposition.
• The Path Constraint constraints the position of a layer to any Bézier path (CC2018 and up only)
• The Position Constraint links the position of a layer to the positions of other layers.
• The Orientation Constraints links the rotation of a layer to the orientations of other layers.
• The List tool is a nice way to combine animations or expressions on the same property.
• The Zero is a layer used to zero out transformations of another layer.