They’ll show you information like how many external links the site has, the number of Facebook and Google+ shares, estimated visits per month, and its page authority. All of this is valuable intel that can give you insight into where your page could potentially rank against them, without needing to do more research with a separate tool or on another page.
Long Tail Pro is a very useful piece of software for long tail keyword research.  One of its best features is that you can carry out heavy analysis on the keywords of your choice, without being limited to only working with one or two at a time. It can provide you also with vast numbers of longtail keywords, or you can apply filters to find the precise keywords to fit your bill.  And you can check your rankings at the same time!

As for the history of the company, as I explained, I created Long Tail Pro back in 2011.  At the time, I was creating tons of niche sites and was doing alot of keyword research and content creation.  I was trying to figure out what types of keywords would rank quickly in the search engines, specifically Google, and I was frustrated with the other keyword research tools (in particular Market Samurai) out there.