From Wikipedia.

Selected Q codes were soon adopted by amateur radio operators. In December 1915, the American Radio Relay League began publication of a magazine titled QST, named after the Q code for “General call to all stations”. In amateur radio, the Q codes were originally used in Morse code transmissions to shorten lengthy phrases and were followed by a Morse code question mark (··— —··) if the phrase was a question.

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, or to break in on a conversation QSK is often used even on VHF and UHF frequencies. (See also Informal usage, below.) Q

Q-Code Description
QRK The readability of your signals (or those of …) is … (1 to 5).
QRK? What is the readability of my signals (or those of …)?
QRM I have interference.
QRM? Do you have interference?
QRN I am troubled by static.
QRN? Are you troubled by static?
QRO Increase power.
QRO? Shall I increase power?
QRP Decrease power.
QRP? Shall I decrease power?
QRS Send more slowly (… wpm)
QRS? Shall I send more slowly?
QRT I am suspending operation. /shutting off the radio
QRT? Shall I cease or suspend operation?/ shutoff the radio
QRV I am ready.
QRV? Are you ready?
QRX Please standby / I will call you again at … (hours) on … kHz (or MHz)
QRX? Shall I standby / When will you call me again?
QRZ You are being called by … on … kHz (or MHz)
QRZ? Who is calling me?
QSB Your signals are fading.
QSB? Are my signals fading?
QSL I am acknowledging receipt.
QSL? Can you acknowledge receipt?
QSO I can communicate with … direct (or by relay through …).
QSO? Can you communicate with … direct or by relay?
QSY Change to transmission on another frequency (or on … kHz (or MHz)).
QSY? Shall I change to transmission on another frequency?
QTH My position is … latitude…longitude
QTH? What is your position in latitude and longitude (or according to any other indication)?