A flat tire occurs when a vehicle's tire loses air pressure, making it unable to support the weight of the vehicle. This can happen due to various reasons, such as a puncture from a sharp object, a slow leak, or damage to the tire itself. When a tire is flat, it can affect the vehicle's handling and safety, making it difficult to drive. To fix a flat tire, drivers often need to replace it with a spare tire or repair it using a patch or sealant. Regularly checking the air pressure and inspecting tires for damage can help prevent flat tires. Proper maintenance of tires, including those on vehicles like cars and bicycles, is essential for safe driving.