Next to the title of a Post, Video, and Collection is number to indicate the rating of the content. If you find the content useful, select 'up' above the number to increase it's rating by 1. If you don't find the content useful, select the 'down' below the number to decrease it's rating.
When you are a Post Video and Collection overview page, at the top right is a way to filter content by 'Most Rated'. Use this to see the content that has been validate as most useful by your peers. From this view you can also see the overall score of the content indicate by the number next to the thumbs-up icon.