Call to action (CTA)
Also called: CTA, Primary action
The main button that asks the user to take the key action on a screen, like Place order or Sign up.
Definition
The CTA is the most important action on a screen and is usually the most prominent button. A screen should have one clear primary CTA. Testers check it is visible, reachable above the keyboard and not hidden by banners or sticky bars.
In practice
On a product page the CTA is "Add to cart". If a cookie banner covers it on small phones, users can't buy anything.