QRZ is an abbreviation used by Morse code users and ham radio operators to express either the statement, "You are being called by," or the question, "Who is calling me?" This abbreviation and other Q-codes were first used in the 1910s.
Q-codes are used as a shorthand among amateur radio operators. The transmitter's tone as well as when the abbreviations are used affect how they are interpreted by the listener. For example, if a listener receives a message from an anonymous transmitter and responds with only QRZ, the anonymous transmitter understands this to ask, "Who is calling me?" The anonymous transmitter then responds with QRZ followed by his identity.