What does a “QSL card” signify?

A QSL card serves as a confirmation of a successful communication between two amateur radio operators. When operators exchange QSL cards, they are essentially verifying that they have made contact, often noting the date, time, band, and mode of communication. This practice has historical roots, as it allows operators to keep a physical record of their contacts, also known as "logs." QSLing is an important aspect of amateur radio culture, with many operators collecting these cards as a way to celebrate achievements like working different countries or regions.

The other options are related to different aspects of amateur radio but do not accurately describe the purpose of a QSL card. A frequency confirmation may involve a request for clarity but does not pertain to the verification of a contact. License renewal notices pertain to regulatory aspects and keeping an amateur license active, while notifications of equipment malfunction address technical issues rather than communication verification.