Prestegjeld. The forum researchers can explain more I'm sure, but below is a link to a "prestegjeld" definition on Wikipedia: http://en.wikipedia.org/wiki/Prestegjeld
I think of a prestegjeld as a clerical district area. It usually contains several smaller parishes or smaller chapels. Very few prestegjeld names are duplicated in Norway and even if the spelling has been altered through the years after emigration can usually be identified fairly easily.
If you have the name of a prestegjeld which your ancestors came from then you are in LUCK! That is among the most important pieces of information you can start with in your investigation. If you've got persons name(s), vital dates such as when born and the name of the clerical district then it should be possible to locate the correct records.
The term "prestegjeld" (abbreviated prgj.) means "parish". Since 2004; the term "prestegjeld" as an administrative unit has been phased out by the Norwegian Church, and is not used anymore. It was formerly a geographical, administrative area of the Norwegian Church. The parish/prestegjeld borders were in 1837 used as a rule when Norway was divided into municipalities, so you can consider a former prestegjeld to be of the same size as todays municipalities. (Although many borders have been adjusted since.)
Norway is today divided in 19 counties and 428 municipalities.