They’ll show you information like how many external links the site has, the number of Facebook and Google+ shares, estimated visits per month, and its page authority. All of this is valuable intel that can give you insight into where your page could potentially rank against them, without needing to do more research with a separate tool or on another page.
Note: If you can’t justify using Ahrefs on a monthly basis, you could sign up for a month, do your KW research and cancel. That said, if you can justify the monthly pricing it’s well worth keeping because you’ll get access to the ongoing functionality such as rank tracking and web monitoring. It also means there’s no need to use any other tools to track rankings or monitor mentions on the web.
Keyword Overview looks at the entered term on its own and addresses expected searches per month, the difficulty of competing against Page 1 results for the same term, a rough estimate of organic click-through opportunities (versus paid ads and non-organic positions on the search engine results page), and the perceived priority that the user should assign to optimization for this term, where the higher the score, the higher the demand and a lowered level of competition.
Provides links to price estimate tools from Google AdWords. That Google AdWords tool showed the necessary bid to rank #1 for 85% of queries, and roughly how much traffic you could expect AdWords to send you based on that bid price and ad position, though, as mentioned above, Google has obfuscated their data in their interface for everyone but longtime AdWords advertisers.
This is another free tool for keyword research. The tool allows you to combine your keywords in a very easy manner. It has three main match types which include broad match, phrase match and the exact match. You can choose on any of them depending on your keyword search objectives. In addition, you can either use broad modifier or optional keyword or both. Most users are finding it to be a very useful tool in their search for the most appropriate keywords.
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.