CTR or Click Through Rate simply means the average number of people clicking on the link you have specified or call to action buttons on advetisements, email campaign and other online source.
For example, You are advertising an AD in a search engines, and if 100 people views your ad but only 4 people clicks on the link and enter your site. Then your click through rate or CTR might be 4%.
In internet marketing, the click-through rate (CTR) is the level of people view a site page and who click on a particular ad that shows up on the page. Active visitor clicking percentage gauges how fruitful a promotion has been to catching client advantage. The higher the active visitor clicking percentage, the more effective the promotion has been in producing interest. A high active visitor clicking percentage can help a site proprietor to earn profit.
Read about Backlinks in SEO >>