For example, if your site vasya.ru is also available at the addresses vasia.ru and vasi.net, then, registering vasya.ru, you can add to the synonyms vasia.ru and vasi.net.
Some synonyms are handled automatically: with the string www. вin the beginning of the address, with some “coding” notations (koi8-r, cp1251 and others), with port number in the server name; these synonyms must not be indicated, if even you do indicate them, the system will remove them from the list.
If you site has “mirrors, you can add addresses of these “mirrors” to synonyms. For example, if your site before was placed at the address home.ru/vasya/, and now it is “moved” to vasya.ru, then pages on home.ru/vasya/ are still visited, you can add this old address to synonyms.
If you entered a synonym, clicked the button “further”, and this synonym has disappeared from the list, then this synonym is automatically transformed into registering site address, or site with such address is already registered.