There are mainly two types of tools—free and commercial. We will first discuss the free tools.
Let's start out simple, by going to Google's AdWords tool.
This tool is available at https://adwords.google.com/select/KeywordToolExternal. It is a great tool to use—just check if your results are for the right language and country, and then fill in your keywords. You can find those options and alter them by using the screen just above the input table. Then type the characters shown to you and hit Get keyword ideas and look how Google gives you information about:
After you run the tool, take a closer ...