Keyword Researcher is designed to search the Autocomplete databases of Google, YouTube, and even Amazon.com. That's a lot of keyword sources! As you probably know, if you're building an authority site, or if you would like to become a dominant player in your niche, then starting with a large database of keywords (that your customers are actually typing in) is a powerful marketing tool.
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.