CTR, or click-through rate, is a measure of the effectiveness of an online advertisement or link, calculated by dividing the number of clicks on the ad or link by the number of times it was shown. It is a crucial metric for digital marketing, as it reflects the percentage of people who were enticed enough by the ad to click on it and potentially become a customer. A high CTR indicates that the ad is resonating with the target audience and driving traffic to the desired destination, while a low CTR may suggest that the ad needs to be revised or the targeting needs to be adjusted. In short, CTR is a key indicator of the success of an online campaign and a valuable tool for optimizing marketing strategies.