Closes all files and terminates EditPad completely.
If you have enabled EditPad's icon next to the system clock in the System Preferences then File|Exit is not the same as clicking the X button in the upper right corner. Clicking the X button keeps EditPad in memory and keeps the icon visible, enabling EditPad to pop up instantly next time you want to edit a file. File|Exit removes the icon and shuts down EditPad completely.
If the icon next to the system clock is disabled, clicking the X button is the same as using File|Exit.