A keyword research tool that is a part of Google Ads service. You can use it in two ways. Get keyword ideas based on words, phrases or a URL related to your business. Or, you can use your existing keyword list and get data for it including average search volume for the last year and the expected number of clicks and impressions for the next 30 days.
It can be used for free. All you need to do to access it is choose Tools > Keyword Planning on https://ads.google.com