A modal window is any type of window that is a child (secondary window) to a
parent window and usurps the parent's control. It is commonly associated with an
Internet Web site
pop-up
window that stays in front of the original window. A user may not
press any controls or enter any information on the parent window (the original
window which opened the modal) until the modal has been closed. A modal window
is commonly used when the author wants to retain the user's focus on the
information in the modal as it is impossible for the user to interact with the
other windows of the same process.