What does the Q signal “QSL” mean?

Q signals are three-letter codes originally developed for telegraphy to standardize common phrases and speed up communication. Among these, 'QSL' is one of the most widely used and translates to 'I acknowledge receipt' or 'I have received and understood.' This foundational meaning is exactly why amateur radio operators exchange physical postcards or electronic records to confirm a contact; they are acknowledging the successful reception of the signal, hence the term 'QSL card.' Other Q signals cover different operational needs. For instance, asking a station to 'send slower' is 'QRS', and asking someone to 'change frequency' is 'QSY'. Remembering that 'QSL' means acknowledgment will help you separate it from these other commands.