Serbia has two autonomous provinces: Vojvodina and Kosovo and Metohija. Serbia "proper" is called Central Serbia. It is called like that for statistical and adminstrative reasons, not being an entity. City of Belgrade is also part of Central Serbia.
Autonomous provinces Vojvodina and Kosovo and Metohija have special jurisdictions, as well as right to use their own symbols. Vojvodina adopted its arms and flag, and uses them. Autonomous province of Kosovo and Metohija is under the administration of United Nations, officially uses symbols of UN. Unofficialy, Albanian citizens consider flag same as that of neighbouring Albania as their ethnic flag. Serbian citizens honours and uses symbols of Republic of Serbia, and Serbian state institutions use them officially.
According to Law of territorial organization and local self-government, administrative districts are regional centers of state authorities. Ministries administer state affairs of Republic of Serbia through centers of districts.
These territorial units are parts of state administration, so they don't have any symbols. They use arms and flag of Republic of Serbia
Municipalities and cities are basic local governing units.
Cities are units with more than 100000 inhabitants, exceptionally even less, if other relevant conditions are gained. Cities could be further divided in civic municipalites (Belgrade and Niš examples). Territorial units with status of city are: Valjevo, Vranje, Zaječar, Zrenjanin, Jagodina, Kragujevac, Kraljevo, Kruševac, Leskovac, Loznica, Niš, Novi Pazar, Novi sad, Pančevo, Požarevac, Priština, Smederevo, Sombor, Sremska Mitrovica, Subotica, Užice, Čačak and Šabac.
Municipalities and cities have right to adopt and use their own symbols. Usage, adoption, sometimes description and blazoning, are regulated by statutes or special decisions about them. Sometimes, municipal or city statutes mention their existence, but municipalities/cities neither use them, nor their description exists. On the other hand, some municipalities/cities have only partial description in their statutes, so their appearance is hard to reconstruct. Municipalities/cities with detailed blazon (description) of symbols are finest examples.
Populated place is part of municipal or city territory with own basic infrastructure, resitential and industrial objects. They can be organized in local communities.