This feature is useful for filtering out results that have tags you are absolutely not interested in. A site's "similarity" is determined by how well its tag signature matches the tag signature that is being searched for. Click on the tags to edit them, and use the sliders to adjust their importance. To add a tag to this list, click "add tag" or click on any tag in a result. The deeper the color of the tag , the more frequently the website is tagged as this. The popularity of a website is, well, pretty much self explanatory. This slider determines how the matched sites are sorted.