| At first, this was the name given by others to the country which called itself the "Federal Republic of Yugoslavia" after the breakup of the Yugoslavia which had existed from World War I to the 1990s. For about a decade, this name was used by countries who took the official position that the former Yugoslavia broke up and none of its component republics was a successor to the name.
The country was made up of former Yugoslav republics Serbia and Montenegro, obviously. Montenegro is much smaller, and has coastline on the Mediterranean Sea, while Serbia by itself is landlocked; some have said that this is a major reason why Serbia stayed united with Montenegro. The agreement brokered by the European Union in March 2002 gave Montenegro the option to leave the union in three years, leaving Serbia as the successor state of the previous government. And Montenegro declared independence from Serbia on June 3, 2006, so "Serbia and Montenegro" no longer exists as such.
Sources:
avalyn
Blush Response
http://news.bbc.co.uk/hi/english/world/europe/newsid_1874000/1874523.stm
http://www.sltrib.com/07052002/nation_w/751091.htm | 
