Call to action (marketing)
A call to action (CTA) is a marketing term used extensively in advertising and selling. It refers to any device designed to prompt an immediate response or encourage an immediate sale. A CTA most often refers to the use of words or phrases that can be incorporated into sales scripts, advertising messages or web pages that encourage consumers to take prompt action.
In marketing, a call to action (CTA) is an instruction to the audience designed to provoke an immediate response, usually using an imperative verb such as "call now", "find out more" or "visit a store today".  Other types of calls-to-action might provide consumers with strong reasons for purchasing immediately such an offer that is only available for a limited time (e.g. 'Offer must expire soon'; 'Limited stocks available') or a special deal usually accompanied by a time constraint (e.g. 'Order before midnight to receive a free gift with your order'; 'Two for the price of one for first 50 callers only'). The key to a powerful call-to-action is to provide consumers with compelling reasons to purchase promptly rather than defer purchase decisions. A CTA can be a simple non-demanding request like "choose a colour" or "watch this video", or a much more demanding request. An obvious CTA would be a request for the consumer to purchase a product or provide personal details and contact information.
Many marketing materials such as brochures, flyers, catalogs, email campaigns etc also make use of a call-to-action. Such instructions are designed to show consumers how to take the next step and create a sense of urgency around the offer. 
Successful sales representatives have long recognised that specific words and phrases elicit desirable responses from prospects and soon learn to incoporate the best lines into effective sales scripts. Clever sales pitches often incorporate a series of small CTAs that lead to a final CTA. These smaller CTAs create a pattern of behaviour that makes it easy for the audience to follow-through with just one last CTA, completing a more demanding request, had it been asked without context. An example could be the purchase of a designer torch. The sales person might ask the consumer to choose a style, then a colour, a size and even a personalised engraving.  When the client views the personalised design, they are more likely to be predisposed to complete the purchase. The sales representative can close the sale by asking, "Will that be cash or credit, today?"
Advertising messages, especially direct-response advertising messages, often make extensive use of calls-to-action. The key to a powerful call-to-action is to provide consumers with compelling reasons to purchase promptly rather than defer purchase decisions. An article in the Wall Street Journal suggests that the incidence of calls-to-action in television advertisements is increasing due to marketer's desire for instant and measurable results. 
In web design, a CTA may be a banner, button, or some type of graphic or text on a website meant to prompt a user to click it, and continue down a conversion funnel. It is an essential part of inbound marketing as well as permission marketing in that it actively strives to convert a user into a lead and later into a customer. The main goal of a CTA is a click, or a scan in the case of a qr code, and its success can be measured via a conversion rate formula that calculates the number of clicks over the times the CTA was seen. Another way to test the effectiveness of a CTA is using A/B testing where several graphics are presented to users and the graphic with highest success rate becomes the default. 
- Eisenberg, B., CALL TO ACTION: Secret Formulas to Improve Online Results, Nashville, Tennessee, Thomas Nelson, 2006, p. 20
- Horner, T., "Writing a Better Call to Action," Marketing Professors, <Online: http://www.marketingprofs.com/articles/2012/7772/writing-a-better-call-to-action>
- Niblick, J., The Profitable Consultant: Starting, Growing, and Selling Your Expertise, Wiley, 2013,
- Steinberg, B., "'Call to Action' Ads Give Clients Results They Can Measure," Wall Street Journal, 22 March, 2005, <http://www.wsj.com/articles/SB111145597859585890>
- Liflander, R., The Everything Online Business Book: Use the Internet to Build Your Business, Holbrook, MA, Adams Media, 2000, p. 25
- Bashinsky, A., "6 Easy Ways to Incorporate Emotional Appeals Into Your Website's Call to Actions," Entrepeneur, 13 January, 2016, <Online: https://www.entrepreneur.com/article/253284>