I love Moz’s interface and how they give you data on the keywords. It’s easy-to-read, making it an ideal solution for both experts and newbies alike. They’ll show you both numeric and visual representations of a keyword’s monthly search volume, its opportunity for ranking, priority, and difficulty. They’ll also show you keyword suggestions and SERP analysis, which is fantastic and detailed.
Most keyowrd databases consist of a small sample of the overall search universe. This means keyword databases tend to skew more toward commercial terms and the core/head industry terms, with slighlty less coverage of the midtail terms. Many rarely searched for longtail terms are not covered due to database size limitations & lack of commercial data around those terms. Plus if those terms were covered, there would be large sampling errors. Google generates over 2 trillion searches per year and claims 15% of their searches are unique. This means they generate searches for over 300 billion unique keywords each year. The good news about limited tail coverage is it means most any keyword we return data on is a keyword with some commercial value to it. And with Google's Rankbrain algorithm, if you rank well on core industry terms then your pages will often tend to rank well for other related tail keywords.
This keyword tool was built on a custom database we have compiled over the past four years. We researched data from the (now defunct) Google Search-Based Keyword Tool and also looked at a few more recent data snapshots to refresh the database and enhance our keyword coverage. Our database contains 28,527,279 keywords representing 13,762,942,253 monthly searches. Our database is primarily composed of English language keywords.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input. In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).