What is "CRT"?

Click-through rate (CTR) is a way of measuring the success of an online advertising campaign for a particular website as well as the effectiveness of an email campaign by the number of users that clicked on a specific link.
The purpose of click-through rates is to measure the ratio of clicks to impressions of an online ad or email marketing campaign. Generally the higher the CTR the more effective the marketing campaign has been at bringing people to a website. Most commercial websites are designed to elicit some sort of action, whether it be to buy a book, read a news article, watch a music video, or search for a flight. People generally don't visit a website with the intention of viewing advertisements, just as people rarely watch TV with the purpose of consuming commercials.

Marketers want to know the reaction of the web visitor. Under current technology, it is nearly impossible to fully quantify the emotional reaction to the site and the effect of that site on the firm's brand. One piece of information that is easy to acquire, however, is the click-through rate. The click-through rate measures the proportion of visitors who initiated action with respect to an advertisement that redirected them to another page where they might purchase an item or learn more about a product or service. Here we have used "click through rate" on the advertisement (or link) because this is the generally used term, although other interactions are possible.

For more informations click here