NOTE, in 2020, the HTML title element you choose for your page, may not be what Google chooses to include in your SERP snippet. The search snippet title and description is very much QUERY & DEVICE dependent these days. Google often chooses what it thinks is the most relevant title for your search snippet, and it can use information from your page, or in links to that page, to create a very different SERP snippet title.
QUOTE: “While, as a whole, web usability has improved over these past several years, history repeats and designers make the same mistakes over and over again. Designers and marketers continuously need to walk a line between providing a good user experience and increasing advertising revenue. There is no “correct” answer or golden format for designers to use in order to flawlessly reach audiences; there will inevitably always be resistance to change and a desire for convention and predictability. That said, if, over the course of over ten years, users are still lamenting about the same problems, it’s time we start to take them seriously.” Therese Fessenden, Nielsen Norman Group 2017
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.