A webcam operates strictly as an input device. Its primary function is to capture video and, in some cases, audio data, which it inputs into a computer system for processing or transmission. Unlike other devices listed, a webcam does not have output capabilities; it only sends data to the computer.
Reference:
In the CompTIA IT Fundamentals study materials, different types of hardware components are classified according to their roles, and webcams are explicitly categorized as input devices, used for video conferencing, security monitoring, and other similar tasks.