Let's say you're considering starting a new website, or venturing into a new product niche. And, suppose you'd like to somehow determine how much search buzz is currently hovering around this topic. You can use Keyword Researcher to get a "feel" for how much interest is actually out there. For example, let's say you were selling cameras. Then you might consider the following:
* Please note our tool currently assumes Google having ~ 83% of the market, with Bing + Yahoo! splitting the remaining 17% of the market. Actual market conditions may vary significantly from that due to a variety of factors including: search location, search market demographics, how much marketshare mobile search has relative to desktop in that particular vertical, etc.

Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website.  In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC).  I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.