A boom operator is an assistant of the production sound mixer. The principal responsibility of the boom operator is microphone placement, usually using a boom pole (or "fishpole") with a microphone attached to the end (called a boom mic), their aim being to hold the microphone as close to the actors or action as possible without allowing the microphone or boom pole to enter the camera's frame.
I feel like sometimes, anons reach for proofs.
Boom.