You don’t really need to worry about the volume size either. Too big a number just means you will have to work harder to get ranked in Google. It’s now quite commonplace to see SEO people say it’s best to just go with your gut feeling on a keyword. Just go for something you would type into Google search yourself instead of beating yourself up trying to find that ‘one’ killer keyword.
Long Tail Pro is a keyword research tool. Keyword research helps you find exact keywords that people are actually searching for. Some keywords are high competition (meaning it is harder to rank for on your site) and some have lower competition (easier for you to rank). How does Long Tail Pro work? First it finds the actual keywords for you based on the ‘seed keywords’ that you input. Then it helps you analyze the competition to see which keywords will be harder or easier for you to rank. How does this benefit you? You can take those ‘easier to rank’ keywords and use them in your content to increase search engine traffic to your site.

This is one of the best articles on Keyword research tool that I have encountered. However, To add more to this, I just wanna point out a tool (LSI Graph) for an outstanding long tail & semantic keyword research. After the recent Google algorithm, Google is now, however focussing more on context & semantics than keyword alone. What do you think about it?
I actually don't use any keyword tools aside from Google Trends, but only rarely do I even use that. I try to talk to many of our target audience members (entrepreneurs) as I can. I attend events, I have phone calls, I sit next to them while working. Generally speaking, I think it's a waste of time to START with keyword tools instead of actual customers. Yes, you can target people in broad swaths and get a high level sense for what's interesting and trending, but at least in the case of our business at NextView Ventures, it's way more powerful to talk to actual "customers" you serve.
I use Ahrefs to find ideas for keywords to add into content, and content to create around keyword opportunities. I like how Ahrefs shows keyword difficulty, search volume, traffic potential (how much organic search traffic it’s possible to get when you rank #1 for a parent topic keyword) and lets you group keywords together to create lists. It’s really useful.
"I've used many keyword tools over the years and Keyword Researcher is up there amongst the most useful of them. Apart from being a great way to get ideas for content, as an AdWords consultant, I also use it to uncover words and phrases that my clients would not want to be bidding on (negative keywords). This is a real time saver for me and a budget enhancer for my clients! All in all, this is a great app and should be used by any professional search engine marketer."
I want to share how and why I sold the company in order to both educate and inspire potential software entrepreneurs.  I certainly don't know everything and obviously companies sell for much more than I sold Long Tail Pro for (I won't be featured in Tech Crunch anytime soon); however, I'm willing to share what I have learned and hopefully that can be beneficial to a few of you.