"The languages referred to as "Bosnian" "Croatian" and "Serbian" are one common language, albeit with different dialects."--BBC
Serbian, Bosnian, and Croatian are all close relatives belonging in the South Slavonic group of languages. They are all mutual intellegible standard varieties of Serbo-Croatian language. Before 1990, they were languages of then collasped former Socialist Federation of Yugoslavia(The area covers today's Bosnia and Herzagovia, Croatia, Kosovo(not recognized by Serbia and Serbs in Bosnia. They claimed it to be Serbian territory), Montenegro, North Macedonia, Serbia, Slovenia).
Flag of Bosnia and Herzagovia
Mainly used by Bosniaks in Bosnia and Herzagovina
Flag of Croatia
Mainly used by Croatians in Croatia, Bosnia and Herzagovina, and northern Serbia
Flag of the Republic of Serbia
Mainly used by Serbs in Serbia(including the controversial Kosovo), Bosnia and Herzagovia
Of all the Slavonic languages, these are the easiest for English speakers to master, and are considered some of the easiest of all European languages for English speakers to pronounce.