To visit our site, what phrases have visitors searched for on Google? How do I know?
How do I know than What words do we have on Google's first page?
This can be easily seen if you connect your site to google webmaster accounts for google and bing webmaster account for yahoo/bing. They will show the results under search queries.
In tools such as Ahrefs, Semrush, Serpstat when you insert the domain it will show the keywords ranking according to their database's reach.