A Serb is a member of the people whose home country is Serbia, though Serbs also live in nearby countries in that corner of Europe (the Balkans). The word is a noun (a Serb) and, more loosely, an adjective (Serb names, Serb history). English took it from Serbo-Croatian Срби / Srbi, from an old Slavic word *sьrbъ, and scholars trace that to a very old root meaning “to protect” or “to watch over.” The same old root took another road and became Sorb, the name of another Slavic people. In English, Serb names the person; Serbian often names the language and anything “of Serbia.” People mix these. The word is a quiet people-name when you are saying who someone is. In talk about the wars of the 1990s it can feel heavy, so use it as a name for people, not as a shortcut for politics you do not know.