What is the difference between a betting exchange and a sportsbook legally?

How to use this answer

This answer is based on the mathematical principle or published rule identified in the source below. If the question involves a live betting market, confirm its settlement definition before applying it to a specific bet.

Check the applicable law where the user is physically located and where the operator is licensed. A gambling site that operates lawfully in one country is not automatically permitted to accept or advertise to another.