From the longer Wikipedia page [1]
A powiat (pronounced [ˈpɔvʲat]; Polish plural: powiaty) is the second-level unit of local government and administration in Poland, equivalent to a county, district or prefecture (LAU-1, formerly NUTS-4) in other countries. The term "powiat" is most often translated into English as "county".
A powiat is part of a larger unit, the voivodeship (Polish województwo) or province.
A powiat is usually subdivided into gminas (in English, often referred to as "communes" or "municipalities"). Major towns and cities, however, function as separate counties in their own right, without subdivision into gminas. They are termed "city counties" (powiaty grodzkie or, more formally, miasta na prawach powiatu) and have roughly the same status as former county boroughs in the UK. The other type of powiats are termed "land counties" (powiaty ziemskie).
As of 2008, there were 379 powiat-level entities: 314 land counties, and 65 city counties. For a complete alphabetical listing, see "List of Polish counties". For tables of counties by voivodeship, see the articles on the individual voivodeships (e.g., Greater Poland Voivodeship).