When a website adopts different keywords and phrases between its pages, the ideal outcome would be that each page is receiving a healthy amount of incoming traffic based on the keywords it is using. Having keywords that are both relatively unique to the website and relevant terms to users who are invested in the industry the site covers is generally how a website hopes to elevate its position in SERPs such as those provided by Google.
Obviously, the different keywords that a given website uses would meet with differing levels of success in terms of how frequently each keyword ends up being searched for by Google's users. It is important for any webmaster to know whether the keyword they previously defined as a certain page's guiding theme is actually resulting in a viably large stream of traffic flowing into the site. If the page is not ranking high on SERPs, the owner would need to consider options such as rewriting the page's content with a different keyword in mind.
However, webmasters can never attain precise data on how many times a particular keyword gets searched for on Google because Google would be engaging in a severe privacy concern if it were to disclose such data. This is why SEO marketing experts are needed; while there exist many utilities that attempt to provide vague estimates about a given term's search volume, they are inaccurate enough that SEO experts are needed to interpret the data based on their own experienced insight. It is not uncommon for a tool to claim that a particular term is not getting any searches at all even though the term is clearly being searched enough to warrant its appearances in Google's Autocomplete function.
Among the better examples of utilities that give data related to search volume are Ubersuggest, Keyword Revealer, and Google's own Keyword Planner service. A webmaster can hire an SEO marketer to use such tools and interpret the figures that come up, but the owner can alternatively use the tools personally to slowly gain similar levels of insight over time and avoid the extra expense. For more information click here https://www.reddit.com/r/SEO/comments/bcdcvl/whatisthemostaccuratewaytocheckkeyword/.