This tool was originally created to carry out keyword research for paid campaigns using Google's AdWords platform. However, it can also be used to research organic keywords, providing estimated global/local monthly search volumes for keywords (i.e. their popularity) and their competition (i.e. how difficult they are to rank for) for organic search.
Within a matter of seconds, Long Tail Pro showed me the top 25 Adwords suggestions for my seed keyword, with KC Scores already calculated! After scanning the list, I found a couple of keyword ideas that I wanted to drill further into. One of these was the keyword – legitimate work from home jobs. This keyword by itself would be very difficult to rank for (KC Score of 40) – but the new cloud version of Long Tail Pro allows me to easily grab up to 20 more suggestions based just on this keyword. I clicked the button to do that (as shown in the image below).

If you don't know the difference between head terms and long-tail keywords, let me explain. Head terms are keywords phrases that are generally shorter and more generic -- they're typically just one to three words in length, depending on who you talk to. Long-tail keywords, on the other hand, are longer keyword phrases usually containing three or more words.
Tip: Instead of targeting large keywords (with lots of monthly searches) in one main article – try targeting lots of long tail keywords in lots of different articles. I’ve been having success with this strategy for a long time now – and more recently Spencer and his team at Niche Pursuits have been using this strategy and talking extensively about it.
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.