This makes Google Suggest a relevant source for keyword research, it contains a large amount of organic keywords very closely related to a full or partial keyword and can be used to find additional most searched appending keywords that make the whole keyword less competitive. Google Suggest can be researched through the Google Search website or through a compatible browser for a small amount of keywords but also in large scale using free scraper tools.

It's wonderful to deal with keywords that have 5,000 searches a day, or even 500 searches a day, but in reality, these popular search terms actually make up less than 30% of the searches performed on the web. The remaining 70% lie in what's called the "long tail" of search. The long tail contains hundreds of millions of unique searches that might be conducted a few times in any given day, but, when taken together, comprise the majority of the world's search volume.

KW Finder is similar to the Google Adwords tool; it even pulls up similar results, which aren’t as entirely on-point as the immediate results from SEMrush and Moz. From my experience with KW Finder, the searches are a lot better if you put some time into manually adding in filters like negative keywords and additional keywords you do want to include.
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.