Final answer:
When the mouse arrow is hovered over an option, a Tooltip appears to describe the function of that option. It's a useful feature that provides quick information to the user without additional clicks.
Step-by-step explanation:
When a mouse arrow is held over an option, a Tooltip opens that describes the option's function. The Tooltip is a small, informational box that appears when you hover over an item with your mouse or cursor. It provides quick, handy details about the item's function without needing to click on it. This feature is especially helpful in software applications and operating systems where numerous tools and functions are present, offering immediate insight into what a button or option will do.