This document explains the functionality of the Replace function when exporting an universe.
Every universe has a CUID which is an unique identifier in the Central Management Server (CMS). If a universe is exported to a folder which already contains the same name, it will prompt to either Replace or Cancel. This happens because the name of the universe is same, however the CUID is different for each universe. The Replace option should be used to overwrite the existing universe with the new one.
The Replace option does the following :