What does a psychologist specialize in?

They are trained in a variety of treatment techniques but may specialize in treating certain disorders or working with certain populations. For example, a clinical psychologist might specialize in an area such as substance abuse treatment, child mental health, adult mental health, or geriatric mental health.

Ican only answer your first question, a machine is like a human body because it's a little similar. they both almost work like the same.