People visit pages on your site via many methods: a bookmark, a link, or by searching. Knowing what searches drives people to your site provides a lot of valuable information to you.
If you have a search bar on your site, and the results are displayed within a page of your site, you can use Google Analytics to access visitors search behavior.
Google Search Console is a way to measure your site's search traffic coming from Google. Search Console is a free service offered by Google. You will need to verify ownership of the site with Google.
Search Console provides many reports and graphs that allow you to view all kinds of information about your site.
Learn more about Search Console.