A small box on screen that simulates the equivalent symbol on a paper form. Options in software are often selected with a check box. Clicking the box switches it to its opposite state. If it is off (disabled - no mark), clicking it turns it on (enabled - a checkmark), and vice versa.
Disable or Enable
When a check box contains a checkmark, the function is "enabled," which means it is turned on and active. When the box is empty, the option is not active (disabled).