Ethnic Albanians speak an Indo-European language as old as Latin. Albanian is as different in vocabulary and grammar from Serbian as Italian is from Russian. Since the early 1980s, when ethnic Albanians began agitating for independence from Serbia, many ethnic Albanians boycotted the state educational system in favor of their own schools funded by Albanians living abroad. As a result, many young ethnic Albanians cannot speak fluent Serbian. Serbs, who speak a south Slavic language, rarely learned Albanian.
Mixed marriages are the exception.
The overwhelming majority of ethnic Albanians are Muslims, descendants of Roman Catholics and Orthodox Christians who converted to Islam during 500 years of Turkish rule. Serbs are staunchly Orthodox, following Christian traditions similar to the Greeks, the Russians and the Bulgarians. That depends on whom you ask. That percentage steadily declined, however, thanks to a high birth rate among ethnic Albanians and a steady Serb exodus from the rural province for more prosperous urban areas of Serbia. Serb nationalists blame the communist government for the exodus.