Call To Action (CTA) is a marketing term for the next step a marketer wants the audience or reader to take. It is a prompt on a website that tells the user to take some specified action and helps remove friction in moving the user down the sales funnel. It's the sentence, or button, that closes the deal! It is typically written as a command, such as ‘Sign Up’, ‘Buy Now’, ‘Join Free’, ‘Start Now’, etc and generally takes the form of a button or hyperlink.
It is a key element on a webpage, acting as a signpost that lets the user know what to do next. Without a clear CTA, the user may not know the next steps to take to purchase a product or sign up for a newsletter and is likely to leave the site without accomplishing their task. There can also be multiple CTAs on a page if there are multiple desired actions for the user to take.