An add-on that provides a node based visual scripting system designed for motion graphics in Blender. This tag should be used when asking about how to use the add-on and not when asking about animating nodes in general.

Animation Nodes is a third party addon by Jacques Lucke that describes itself as

A node based visual scripting system designed for motion graphics in Blender.

Animation Nodes (github) is an open source project and is widely used.

Use this tag for questions about the use of animation nodes.