Is a hole saw a circular saw?

"Yes, a hole saw is a circular saw. It is primarlily used to cut through thin materials and is used in a drill. Hole saws, or circular saws, are used to cut wood, plastic, concrete, or stone, depending on the type you have."

A hole saw refers to the bit. Round bit like a piece of pipe, used in a drill, that cuts a hole and leave a donut or plug from the hole instead of an auger or butterfly bit that chips out all of the wood in the hole.

A circular saw is the saw that uses a flat circular blade to cut in a straight line.