A/C, or air conditioning, is a system that cools and dehumidifies indoor air. It works by circulating refrigerant through coils, absorbing heat from the air inside a building and releasing it outside. This process helps maintain a comfortable temperature, especially during hot weather. A/C systems come in various types, including central air conditioning, window units, and portable units. They are commonly used in homes, offices, and vehicles to improve comfort and air quality. Regular maintenance, such as changing filters, is essential for optimal performance and energy efficiency.