Call to action (CTA) is noun. When you create content written or speaking you can have a call to action during it or at the end of your delivery.In marketing it is used all of the time. You want to persuade encourage people to take some type of action when they are consuming your content.

When writing a blog post you may put this example CTA at the end of it or somewhere in it.

P.S. Can we send you an email?

Once a week or so we send an email with our best content.
We never bug you; we just send you our latest piece of content..