A call to action is a clear invitation for someone to do the next useful thing. It is like a sign at a museum that says, “Start the tour here.”
On a website, it might be a “Try it free” button or a link to read more. A good call to action uses words that explain what will happen, so people do not have to guess.
Choose one main next step for each area of a page. If every button is presented as equally important, visitors may not know where to begin.