Magic meaning of Apply button on a form

1. What does apply button mean?
2. What does the Apply button do in Windows?

What does apply button mean?

The Apply button applies the current settings in all of the property pages to the external object, as opposed to applying only the current settings of the currently active page.

What does the Apply button do in Windows?

The Apply button applies the changes to the settings that have been made, but does not close the dialog box. The OK button also applies the changes to the settings, but in addition closes the dialog box. Apply is useful if you are trying out different settings and don't want to have to keep re-opening the dialog box.