Scout is an easy to use extension tool for chrome browsers that turns your website into a significant keyword generator. By a click of mouse, you can uncover relevant keywords in your industry by choosing a website that is successful and attractive to your audience. You will be able to understand the true language of your successful audience and generate keyword ideas that you can use in your marketing strategy.
What I really like about them is extensive detail including the keyword difficulty. Ahrefs uses clickstream data to also show how many clicks you will get from the search engine. This is very useful after knowledge graph integration, as many keywords may have huge traffic but they hardly get any clicks from the search engine. Reason being, they get answers directly from the Google search result. Example of one such query is: “birthdate of any celebrity”
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.