What is the difference between dB and dBc?

Could you elaborate on the distinction between dB and dBc in the context of signal measurement and analysis? I'm particularly interested in understanding how these two units are used differently in the field of telecommunications and electronics. As a professional in the cryptocurrency and finance sector, I'm aware of the importance of precise measurements and calculations, and I'm curious to know how this principle applies to dB and dBc in the realm of signal processing. Could you provide a concise yet comprehensive explanation of the key differences between these two units?