In Keyword Planner, formerly known as the Keyword Tool, you can get search volume and traffic estimates for keywords you're considering. Unfortunately, when Google transitioned from Keyword Tool to Keyword Planner, they stripped out a lot of the more interesting functionality. But you can make up for it a bit if you take the information you learn from Keyword Planner and use Google Trends to fill in some blanks.
Understandably – not everybody who buys Long Tail Pro will have the audience or platform to be able to promote as an affiliate. For example – a food blogger’s audience won’t care about a keyword research tool. So even if affiliate promotion won’t work for you – I hope I’ve shown how the tool will more than pay for itself if used for what it is intended for.
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.