Two queries rarely produce the same page. A search for a plumber shows a map with three businesses; a search for a definition shows a snippet; a comparison shows an AI summary and product cards. Knowing the layout of the SERP for a given query tells you what kind of page can win it, and whether a click is even likely.
Reading SERPs is the first step of any SEO plan: it shows which pages Google considers the answer, which formats it favours, and which features sit above the unpaid results. The same reading now includes which queries trigger an AI Overview.