I just have the free version right now so I don't know all that the pro one can do. But even the free version has A LOT of tools you can use, I haven't even figured them all out yet. But one that I have used is their Content Optimizer. You can take a new or existing content piece of yours, and compare it to one of your competitor's pieces on a similar topic, and see where you might be lacking based on the keywords that are used in each piece. 

Depending on your topic / vertical and your geographic location the search engines may have vastly different search volumes. The tool can only possibly offer approximations. Exact search volumes are hard to find due to vanity searches, click bots, rank checkers, and other forms of automated traffic. Exceptionally valuable search terms may show far greater volume than they actually have due to various competitive commercial forces inflating search volumes due to automated search traffic.
Creating a psychologically alluring title is important--because search engines will rank our document (in part) based on how many clicks the title is getting--relative to other articles on Google's Search Results Page (SERP). Hence, a title that has some stylistic panache, will (in theory) ultimately rank higher than a title that doesn't have anything eye-catching about it.
Analyzing the current top 10 search results in Google is the most important part of keyword research. This is where you determine whether or not you can produce a webpage that can beat any or all of those results. The process is known as first page analysis – and it is by far the hardest process to understand and really figure out (especially when you first start out). Don’t worry though – Long Tail Pro has detailed and in-depth instructional videos available that show you exactly how to do this.
Are you a business owner, online marketer or content creator? If so, most likely you would like more people to visit your website, read your content and buy your products or services. The easiest way to achieve it is to find out what your potential customers or readers are searching for on Google and create content on your website around these topics.
In fact, Google Suggest is the best way to find good long tail keywords that people use to find information on Google. Google admits that while Google Autocomplete (another name for the Google Suggest feature) was not designed specifically for marketing, it can deliver meaningful insights and help stay on top of trends. There are also many clever ways to use Google Autocomplete that can help you with SEO.
There, now. We’ve given you an overview of twenty-five cool keyword tools. Of course each of these has its own strengths and caveats, and at least for now, none can match the effectiveness of Google’s Keyword Tool, particularly in language, location, or device-specific results. Google gathers and analyzes vast amounts of data and as you know, the rich only get richer.

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.
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