Final answer:
The oncontextmenu event occurs when you click the right button of a mouse and want to perform a specific action when the user right-clicks on a button.
Step-by-step explanation:
The event that occurs when you click the right button of a mouse is the oncontextmenu event.
When you associate an event handler with a button click, you can use the oncontextmenu event to detect a right-click on the button. This event is specifically triggered when the user interacts with the context menu that appears after a right-click.
For example, if you have a button on a webpage and you want to perform a specific action when the user right-clicks on it, you can attach an event handler to the oncontextmenu event of the button.