International dialing codes are split in to 3 parts; IDD Prefix, Country Code and NDD Prefix. These parts are grouped together in the diagram below as on the site. Hover over the numbers on the main page to see which international dialing code part they belong to.

IDD Prefix (International Direct Dialing)
The IDD Prefix is the international dialing code part used to dial out to a foreign country. It tells the telephone network it is making an international call. For a single country the IDD Prefix is the same no matter which foreign Country Code is dialed. If the phone has a plus symbol this can be dialed instead of the IDD Prefix.

Country Codes
The Country Code follows the IDD Prefix. It is the international dialing code part that identifies the foreign country to connect to.

NDD Prefix (National Direct Dialing)
The NDD Prefix is the dialing code part used when dialing a national number. This is removed when dialing a foreign country and is therefore crossed out in the diagram below. The City Code or Area Code follows the NDD Prefix but the Ndd Prefix and Area Codes are usually displayed together.

Area Codes
Area Codes or City Codes are dialed before the local number.