A cathode heater operates by heating a cathode to facilitate thermionic emission, where electrons are released from the heated surface. The discussion highlights the need for clarity in understanding the specific type of cathode heater being referenced, as the term can be vague. Participants emphasize the importance of context when asking about technical concepts. The conversation suggests that a more detailed explanation is necessary to fully grasp the mechanics of cathode heaters. Overall, a clear understanding of thermionic cathodes and their heating process is essential for accurate comprehension.