This property controls whether or not the user will be able to access it or whether it will just be displayed on the form. If the object is an entry field, such as TTASEnter, the user will not be able to change the value displayed, if it is a button (TButton) they won't be able to 'click' it. This property is used all the time during a program operation. In many cases you might want to 'turn off' an object during a certain program operation, or only turn it on at a specific point in the program. In either case, this is the property to use.
The options are True (checked) and False and can be set at both design and runtime.
See also Visible.