From the Wikipedia page 
Cambodia is divided into 24 provinces (Khmer: ខេត្ត, khaet) (as of January 2014 New Province of Tboung Khmum split off from Kampong Cham Province) and the special administrative unit Phnom Penh (Khmer: ភ្នំពេញ, Phnom Penh). Though a different administrative unit, Phnom Penh is at province level, so de facto Cambodia has 25 provinces and municipality.
Each of Cambodia's 24 provinces is divided into Districts (Khmer: ស្រុក, Srok)- as of 2010 there are 159 districts and 12 districts in Phnom Penh (Khmer: ខណ្ឌ, Khan). Each of the provinces has one capital district (changed to "City/Town", Khmer: ក្រុង, Krong), e.g. for Siem Reap it's Srok Siem Reap. The exceptions are Banteay Meanchey, Kandal, Mondulkiri, Oddar Meanchey, Preah Vihear Province and Rattanakiri, where the province and the capital district does not match together.
District (ស្រុក, srok) of a province is divided into "Communes" (Khmer: ឃុំ, Khum). "Commune" (Khmer: ឃុំ, Khum) is further divided into "Villages" (Khmer: ភូមិ, Phum).
In Phnom Penh the districts are called Khan (Khmer: ខណ្ឌ), and their subdivisions Sangkat (Khmer: សង្កាត់) which are smaller in the other provinces. Sangkat are further subdivided into Phum (Khmer: ភូមិ), which are usually translated as villages, though they do not necessarily cover one single settlement.
See also ]]List of Cambodian districts and sections]]