You can follow users to keep up to date with what they're adding to their hearts. When you follow someone, all of their images appear on your Friends page, so you can see at once what your friends are hearting.
You can visit other people's profile and if you like what they've hearted so far you can also follow them. It's OK to follow people you don't know. It's a good way to make new friends!
To start following someone, go to that user's profile and click on the "Follow" button next to the user's name. After you click you'll be following that person, and the button will change to "Unfollow".
You can also start following someone by clicking on the "Follow" button within an image:
To stop following someone (unfollow) you can go to the user's profile and click the "Unfollow" button: