A call to action (CTA) is a specific instruction meant to prompt a user to perform a specific task. Usually in the form of a banner, button, or some type of graphic or text, they are used to drive visitors down a conversion funnel. Calls to action can (and should) be tested & monitored so they can be refined to generate higher conversion rates. Call to action should be clear and relevantly worded for best effect.
“Call Now”, “Get a Quote”, “Request a Callback”, “Download our Whitepaper” are all calls to action.
“Click Here” is, technically, a call to action but it is not very persuasive and doesn’t really cut it when compared to something more specific.