Wikipedia
A sejmik (, diminutive of sejm, occasionally translated as a dietine; ) was the name of various local parliaments throughout the history of Poland. The first sejmiks were regional assemblies in the Kingdom of Poland, though they gained significantly more influence in the later era of the Polish–Lithuanian Commonwealth. Sejmiks arose around the late 14th and early 15th centuries and existed until the end of the Commonwealth in 1795, following the partitions of the Commonwealth. In a limited form, some sejmiks existed in partitioned Poland, and later, in the Second Polish Republic. In modern Poland, since 1999, the term has been revived with the voivodeship sejmik (sejmik województwa), referring to the elected council of each of the 16 voivodeships.
The competences of sejmiks varied over time, and there were also geographical differences. Often, numerous different types of sejmiks coexisted in the same governance structure. Almost always presided over by the marshal of the sejm, sejmiks could often elect delegates to the national sejm, and sometimes could give them binding instructions. Sejmiks attained the peak of their importance at the turn of the 18th century, when they effectively supplanted the inefficient national sejm.