The video shows a close-up of a bicycle's rear wheel and brake system. A person's hand is seen adjusting the brake caliper, which is a part of the brake mechanism. The caliper is attached to the wheel and is used to apply the brake pads to the wheel's rim. The person's hand is using a tool to adjust the caliper, ensuring that it is properly aligned with the wheel. The video provides a clear view of the brake caliper and the tool being used to adjust it.