What is "posadnik"

Posadnik ( Cyrillic: посадник) was the mayor in some East Slavic cities or towns. Most notably, the posadnik (equivalent to a stadtholder, burgomeister, or podestà in the medieval west) was the mayor of Novgorod and Pskov. The term comes from the Old Church Slavic "posaditi," meaning to put or place; they were so-called because the prince in Kiev originally placed them in the city to rule on his behalf. Beginning in the 12th century, they were elected locally.