Skeleton

The term skeleton is normally used to describe the internal frame work of bones and points of articulation in the human or other vertebrates (animals with backbones)
This is actually an internal skeleton or endoskeleton supporting the soft tissues and organs (wet ware).

An external skeleton or exoskeleton is found in many invertebrates such as crabs, lobsters and insects and encloses all the soft tissue and organs (more wet ware ).

A Robot can have either or both types although the terms chassis or frame are more usual.

The Marine Lobster

The chassis approach of many research robots would be classed as endoskeleton with the PCBs between and on the decks of the frame.
In fact although the Crustacean exoskeleton at first glance seems the closest to a robotic solution, the fact that all the joints and strength members completely surround the working parts would prove difficult to construct and maintain.

When the lobster grows it sheds the whole exoskeleton, swells and excretes a new one complete with new articulation joints - maybe there is an idea there!

The Shadow android and the arm use the Airmuscle which more or less demands the endoskeletal route for this type of "mobile" robot

Many of the Telerobotic Arms take the exoskeletal approach where blocks of metal are machined to form the different arm sections and the rams and valves and any electronics are placed within. These arms are usually working in a less controlled environment than the industrial arms and the construction and drive philosophies are as different as robot wars and Lab research robots.