Each page of the website is ranked separately
The most common mistake is to think that everything depends on the website. Although it is easier to explain the functioning of the SEO by talking about the website in general and most people only expect to see their website on the first page of results for a particular keyword, they do not pay attention to which page is related to that result.
In many cases, one page of your website has good results for several keywords that aren't even related, and this isn't too much of a problem - in a way!
If you're selling a product and want to optimize for a particular keyword, you wouldn't want users to see your contact page instead of the product page in search results.
To make this easier to understand, each page of your website should be optimized for multiple related keywords.