The quality of a restaurant is typically rated on a scale of from one to four stars, with four being the best. A few ranking systems, however, use a one-to-five star scale. Regardless, the term Four-star restaurant means a restaurant of the highest quality.
The Michelin Guide is a famous granter of ratings that uses the three star system. AAA uses a 4 diamond rating.
As a side note, the one-to-four star rating scale is also commonly used for films as well.
