A Call-to-Action, often abbreviated as "CTA" is a button, banner or other graphic element that catches the user’s attention and entices them to take action using imperative words.
For example, a “Buy now!” button looks clickable and is brightly colored to stand out from the rest of the website. It instructs the user to take the action of purchasing the product.
Call-to-Actions are an important part of marketing as it is designed to show consumers how to take the next step and it also creates a sense of urgency. Successful CTAs provide good, compelling reasons for the customer to proceed with the purchase promptly rather than wait and consider.