This is a nice trick to quickly filter data with only a couple of clicks, especially if you're not exactly sure what you're looking for. Say, for example, that you need to find a company and you can't remember their name but you know they're based in PA. Instead of doing an Advanced Find, setting up your filters and columns, etc., you can sort and filter a view in place.
First you would go to the Accounts area and select the view you need. In this example, I want to see all accounts and I need a column for state. Click on the state column so that the view is sorted by state. Then choose the letter 'P' at the bottom of the page to see only states beginning with 'P'. Done!