What's the difference between the star and the heart?
To star something is to measure its quality. To heart something is to emote it.
What is the star icon used for?
An asterisk is a star-shaped symbol (*) primarily used to call attention to a footnote, indicate an omission, point to disclaimers (which often appear in advertisements), and dress up company logos. An asterisk is also often placed in front of constructions that are ungrammatical.