The Discovery is the place to display the trending/popular updates you may interested in to follow.
Feeds: displays trending posts, the most popular (based on total likes and comments) ones will on top.
User trending widgets: this widget randomly display the most popular users (based on number of followers) for you to follow.
Hashtags trending widgets: this widget randomly display the most popular hashtags (based on number of posts that has the hashtags inside) for you to follow.