Score (or Points) is one of the fundamental elements in Blossom Blast Saga. It's a stat value that's calculated during the level playing and after the level has been completed. Every level has a score requirement which is needed to be reached so that a player can pass it. Stars are obtained based on the score you have at the end of a level. Score requirement for 1 star is needed as a minimum to pass the level.
However, each level typically has additional tasks for players to do in order to pass a level, besides the score requirement.