To optimize a particular page, you need to know what phrases your customers are using to look for what you have to offer.
The best way to get data about keywords is from the Google Ads Keyword Planner- if you have access to it.
An important part of keyword research is using data to evaluate which phrases you should focus on. Google Trends is a good way to do this for free.
Keyword research is the process of finding the phrases your customers use, to find companies like you in the search engines.