Human scabies is caused a microscopic scabies mite which burrows into the upper layer of the skin where it lives and lays its eggs. The most common symptoms of scabies are intense itching and a pimple-like skin rash. The scabies mite usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies.
Learn more about scabies from the CDC Web site and view the life-cycle of the scabies mite and the areas where they are usually found on the body.
This interactive tutorial from Medline will answer all of your questions about scabies. The tutorial is also available in Spanish.
The American Academy of Dermatology also has extensive information about scabies.