Various prefix types

There are many different types of prefixes when it comes to telephony. These are the most important ones to recognize:

Prefix for call out (PBX prefix)	Often 0 or 00 The prefix used to get a line out from a PBX.
Local area prefix	The prefix that all local area numbers, such as 018 or 08, begin with. In Sweden and many other countries the figure 0. For international calls no local area prefix is dialled. Mostly used in countries with an open number plan.
Extension prefix	The PBX extensions within a location become complete subscriber numbers with an extension prefix. A location with the extensions 2900 and 2901, whose corresponding subscriber numbers are 102900 and 102901 have the extension prefix 10.
International prefix	The prefix used to specify that you want to call from the current country to some other country. 00 from Sweden.