When you mute the animation channels of an object, a mute node is automatically created in the dependency graph for each muted channel. You can view the mute node in the Hypergraph. The muted channels input to the mute node, and the mute node outputs to the object.
In the Channel Box, the mute node appears with a name like mute_objectn_channel (where n represents the number of the object if there is more than one of the same type in your scene). Example mute node names include: mute_pCube1_translateX, mute_joint1_rotateZ and so on.
When the Mute attribute is set to on, all animation nodes that connect to the mute node are muted. When the mute node is set to off, all animation nodes that connect to the mute node are not muted. Setting the mute node to off in the Channel Box does not remove it from the scene hierarchy.