Click Through Rate (CTR): The Click Through Rate (CTR) is a metric that measures the number of clicks advertisers receive on their ads per number of impressions. It is a critical measurement for understanding the efficiency and effectiveness of a specific marketing campaign or advertisement. It's calculated by dividing the total number of clicks by the number of impressions (views) and multiplying by 100 to get a percentage. This helps to understand how well your keywords, ads and landing pages are performing from a user engagement perspective.