From the Overview: "The Republic of Kosovo declared independence from Serbia in 2008, nearly a decade after the end of a brief but lethal conflict between Serbian forces and a Kosovo Albanian insurgency led by the Kosovo Liberation Army (KLA). Since 2008, Kosovo has been recognized by more than 100 countries. The United States and most European Union (EU) member states recognize Kosovo. Serbia, Russia, China, and various other countries (including some EU member states) do not. The United States has strongly supported Kosovo's state-building and development efforts, as well as its ongoing dialogue with Serbia to normalize their relations. Kosovo regards the United States as a security guarantor and key ally."
CRS Report for Congress, R46175
Congressional Research Service: https://crsreports.congress.gov/