Search Click-Through Rate
The ratio of clicks on your ad (for SEM) or link in organic results (for SEO) to the number of total views. A higher CTR means that more people who see your link are clicking on it, indicating its relevance to the search query.
(Number of Clicks / Number of Views) x 100
If an ad is displayed 1,000 times and clicked on 50 times, its CTR is 5%.