Keyword research tools and softwares are dedicated online tools which, for a given generic keyword, list hundreds or thousands of keywords used for search engine queries. Their purpose is to suggest keywords for SEO and PPC campaigns.
Some keyword tools are free functions integrated in PPC search engine platforms. The most known is AdWords keyword tool.
Some other free or paid dedicated tools or softwares may offer more keyword results and are used for implementing long-tail keywords campaigns.
An example of dedicated keyword research tools for identifying long-tail keywords: