Copy Animation to Selected works in the same way things like properties, materials, modifiers, and constraints do in Blender: you select all of the objects you want to share the animation, then make one object the Active object by shift+selecting it. Right click and you’ll see an AnimCopy menu.

Choose Copy Animation to Selected and all of the selected objects will receive the animation data you specify in the Redo Panel.

All

Every F-Curve will be copied

Transform

Only Location, Scale, and Rotation animation will be copied

Selected F-Curves

Only the Active Object’s selected F-Curves will be copied

Selected Keyframes

Only the Active Object’s selected Keyframes will be copied

Copy Modifiers

The Active Object’s F-Curve Modifiers will be copied.

Replace

When enabled, the existing animation data of the selected objects will be replaced by the Active Object’s. If disabled, the keyframes will be merged.

Remap X, Y, Z

sometimes your rig’s controls/bone orientation can differ. Remapping allows you to remap the dimensions.