A SERP is the search results page for a specific query. What it looks like changes with intent, location, device, how current the topic is and other circumstances.
What is a SERP?
A SERP combines unpaid results, ads and special features. That's why the same position on two queries can bring a very different number of clicks.
In keyword research I check more than the order of results. I look at the page types, the dominant format and how much room is left for organic results.
What a SERP is made of
It can contain classic links, AI Overviews, a featured snippet, a map pack, images, videos, products, news or People also ask questions.
The layout isn't fixed. Google tests and adjusts the individual features, so you need to recheck important queries regularly.
Why the shape of the SERP matters
Ads, an AI summary or local results can push organic links further down and change CTR. Average position alone doesn't give you the full picture of performance.
On an informational query, some users end without a click. For a product or service, they need to compare offers, check details or take an action on the site.