QUOTE: “Search engine optimization (SEO) is often about making small modifications to parts of your website. When viewed individually, these changes might seem like incremental improvements, but when combined with other optimizations, they could have a noticeable impact on your site’s user experience and performance in organic search results.” Google Starter Guide, 2020
QUOTE: “Expertise, Authoritativeness, Trustworthiness: This is an important quality characteristic. …. Remember that the first step of PQ rating is to understand the true purpose of the page. Websites or pages without some sort of beneficial purpose, including pages that are created with no attempt to help users, or pages that potentially spread hate, cause harm, or misinform or deceive users, should receive the Lowest rating. For all other pages that have a beneficial purpose, the amount of expertise, authoritativeness, and trustworthiness (E-A-T) is very important..” Google Search Quality Evaluator Guidelines 2019
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.