Muggles' Guide to Harry Potter/Magic/Fire-call

Overview
A fire-call is a specialized use of the Floo Network – when you do not need to be physically present in another location, but you need to communicate with someone there, you insert just your head into a prepared fireplace, and your head is transported to another fireplace.

Extended Description
This technique is first seen in Harry Potter and the Goblet of Fire when Amos Diggory, then at the Ministry of Magic, has urgent need to reach Arthur Weasley regarding some garbage cans that are flying around Mad-Eye Moody's yard. Harry receives a fire-call from Sirius later in the book. It is also used in Harry Potter and the Order of the Phoenix, twice by Sirius to reach Harry, and twice by Harry to try and reach Sirius. Harry feels that this is a very uncomfortable way to send a message; quite apart from the necessity to stay hunched over the fireplace while talking, it is very disconcerting to have your head whirled around dizzily while the remainder of your body remains firmly planted on the floor in front of the sending fireplace.

More information is available at Floo Powder and Floo Network.