From the Wikipedia page 
A voivodeship sejmik (Polish: sejmik województwa), also known as a provincial or regional assembly, is the regional-level elected legislature for each of the sixteen voivodeships of Poland. Sejmiks are elected to four-year terms, decided during nationwide local elections. The size of the legislative assembly varies for each voivodeship depending on the population; in lower populated provinces, there are 30 members, while in the most populous (Masovian Voivodeship) there are 51 members. Elected representatives of an assembly are known as councillors (radni).