Put simply, heart represents a user's score. It is expressed in numerals and will increase as a user receives likes and comments on their designs. The number is publicly available on a user's profile page.

If a user has a high heart score, it should indicate they have created excellent designs that the community likes.

You will also see the heart score in the app on the user's profile page:

Can you do anything with your heart score?

No, it is simply for display purposes only.