A janitor's job involves maintaining cleanliness and order in buildings by sweeping, mopping, vacuuming, and dusting floors, surfaces, and windows; sanitizing restrooms and restocking supplies like soap and paper; emptying trash and recycling bins; performing minor repairs (e.g., changing lightbulbs, unclogging drains); and ensuring building security by locking doors, all while following strict safety guidelines for handling cleaning chemicals and equipment. They report major maintenance needs to supervisors and keep supplies organized, ensuring a safe and hygienic environment for occupants.