Questions about the meaning and customary use of Q-codes.

The original Q codes were created, circa 1909, by the British government to facilitate communication between maritime radio operators speaking different languages and were soon adopted internationally.

As their use grew, some structure was imposed as follows:

QAA to QNZ - Assigned by the International Civil Aviation Organization (ICAO).
QOA to QQZ - For the Maritime Services.
QRA to QUZ - Assigned by the International Telecommunications Union (ITU).

These Q codes were originally used in Morse code (CW) transmissions to shorten lengthy phrases and were followed by a Morse code question mark (‏·‏·‏—‏‏—‏·‏·‏) if the phrase was a question.

However, Q codes are commonly used in voice communications as shorthand nouns, verbs, and adjectives making up phrases. For example, an amateur radio operator will complain about QRM (man-made interference), or tell another operator that there is "QSB on the signal" (fading); "to QSY" is to change your operating frequency.

An extensive list of Q codes can be found here: http://en.wikipedia.org/wiki/Q-codes#Q_codes_applicable_for_use_in_amateur_radio