The click-through rate (CTR) is the share of delivered emails in which someone clicked a link. It's measured with click tracking, which routes each link through the sending tool's tracking address.
CTR in cold email
Most good first cold emails have no link at all: they ask a question and want a reply. So CTR matters only for emails built around a link, such as a booking page, a short video or a case study. There, it shows whether the offer interested people enough to look.
Why it's often inflated
Company security systems click every link to scan it, so some clicks aren't people. A burst of clicks seconds after delivery is usually a scanner.
Better measures
Replies, positive replies and meetings booked. If you do use links, put one, to a page on your own domain, and use a custom tracking domain.