What is the external skeleton and the internal skeleton, explain? What is the difference between them.

Representatives of insects, arachnids, crustaceans and molluscs have an external skeleton. It looks like a chitinous shell or shell impregnated with lime, which provides strength. Serves as the base on which the muscles attach. It tends to remain the same, regardless of the age of its owner. But for growth, molting is necessary – the owner throws it off, thereby remaining defenseless for some time, and therefore an easy prey.
Chordates have an internal skeleton. It consists of cartilage and bone tissue. It grows with the body, no molting is required for renewal. Has properties of strength, plasticity.