DefaultButton

DefaultButton[]
represents an OK button that closes a dialog, and is the default when Enter is pressed in the dialog.

DefaultButton[action]
represents a button that is labeled OK, and whose action is to evaluate action.

DefaultButton[label, action]
uses label as the label for the button.

In dialogs created with DialogInput or CreateDialog, pressing Enter is effectively equivalent to pressing the OK button.

If there are several default buttons in a single dialog, Enter will use the first one in the dialog.

Create dialog input, and use DefaultButton to dismiss dialog: