What's the difference between filtering and sorting?

Filters:  Filters let you narrow results based on parameters such as investigation number, date, or subject.  When you select an option in a filter, the only results that get displayed are the results applicable to the filter you selected.  For example, in the screenshot below, we see our USITC federal register notice page where two filters have been applied:  by type (section 337) and by date (2013).  So, the only notices that appear, once the filters have been selected:

Sorts:  Conversely, sorting doesn't narrow your results, but it does allow you to reorganize the existing results in a manner that makes it easier to find what you want. Sorting is usually done by clicking on any of the hyperlinked column headers on a page. For example, in the screenshot below, we have reorganized the Petitions & Complaints page so that it shows the most recent items based on docket number: