Behance Help Center
Appreciations are a way to send genuine kudos to another creative professional. All projects have a blue "Appreciate This" button at the bottom, below the content. Appreciating a project will add to the project's "appreciation count" and let the member know that you were a fan of their project. One of the ways to sort the Behance gallery is by "Most Appreciated."
If you're logged in when you Appreciate a project, it will be saved and you'll be able to view it later in your "Appreciation Stream," which can be accessed at any time by going to behance.net/USERNAME/appreciations. Projects that your network contacts have Appreciated will show up in your Activity Feed.