in a nutshell
Serbian language (srpski jezik) is used mainly in Serbia, Montenegro,
Bosnia & Herzegovina, Croatia and by Serbs abroad (Serbian expatriates).
The previous standard is known as Serbo-Croatian, which is now split
into Serbian, Croatian and Bosnian language standards.
Serbian language uses two distinct writing systems (alphabets): a variation
on the Cyrillic alphabet, devised by Vuk Karadic, and a variation
on the Latin alphabet, devised by Ljudevit Gaj. The letters of these
two alphabets map to each other one-to-one.
its writing system, Serbian and Croatian follows the principle 'a letter
per sound'. This principle is represented by the saying, "Write
as you speak and read as it is written".