The answer to 'what does tune-up do' is a routine maintenance service for your home's HVAC (heating, ventilation, and air conditioning) system. An HVAC tune-up typically includes a comprehensive inspection, cleaning, and adjustment of all the system's components to ensure it's operating at peak efficiency.
During a tune-up, an HVAC technician will check and clean the air filters, inspect the coils, test the thermostat, lubricate moving parts, and make any necessary adjustments to the system. This helps improve the system's performance, reduce energy consumption, and extend its lifespan.