You can earn 3 stars per level in Candy Crush Saga. The number of stars depends on the score achieved while completing the level: reaching the first score threshold earns one star, while higher scores unlock the second and third stars.
Stars provide a performance measure in addition to the basic win condition. A player only needs to meet the level’s objective to advance, but finishing with extra moves, creating special-candy combinations, and triggering cascades can produce a higher score and more stars. The exact score thresholds vary from level to level.
A frequent misunderstanding is that every level requires three stars to progress. It does not. One star is generally enough to mark a successful completion, while two or three stars show stronger scoring performance. Some special or mixed levels may also have objectives beyond ordinary score-building, so stars should not be confused with the level’s main goal.