Serbian is the standardized variety of the Serbo-Croatian language mainly used by Serbs. It is the official and national language of Serbia, one of the three official languages of Bosnia and Herzegovina and co-official in Montenegro, where it is spoken by the relative majority of the population. It is a recognized minority language in Croatia, North Macedonia, Romania, Hungary, Slovakia, and the Czech Republic.
Standard Serbian is based on the most widespread dialect of Serbo-Croatian, Shtokavian (more specifically on the dialects of Šumadija-Vojvodina and Eastern Herzegovina), which is also the basis of standard Croatian, Bosnian, and Montenegrin varieties and therefore the Declaration on the Common Language of Croats, Bosniaks, Serbs and Montenegrins was issued in 2017. The other dialect spoken by Serbs is Torlakian in southeastern Serbia, which is transitional to Macedonian and Bulgarian. Source : Wikipedia