As you can see, LongTailPro is pulling data from Google Adwords. WHAT?! So LTP uses a mix of their own massive data (launched in 2011) and data pulled via API from Majestic.com, Moz.com, and Google Adwords (http://adwords.google.com). Once you input your seed keywords, LongTailPro outputs suggested keywords related to your seed keywords, search volume, Adwords suggested bid, Adwords competition, total words, rank value, average keyword competition, language searched, and location searched.
"This is the only keyword research tool that I recommend. The ideas, inspiration, and content longtails you will get for your niche topic are going to result in you producing a page of content that is more than going to pay for this tool. And as they are Google's database then we KNOW that these terms are being searched by a decent volume of peeps every month. It's a goldmine dudes."
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.