CTR (Click-Through Rate) is the percentage of people who click your result after seeing it in search. A higher CTR means more traffic from the same rankings.
CTR = clicks ÷ impressions. If 100 people see your result and 5 click, your CTR is 5%. It reflects how compelling your listing is.
It correlates with relevance; strong CTR can support performance, but it is debated as a direct factor.
In Google Search Console under Performance.