The general mechanism of an air compressor is a piston or rotary element (e.g. rotary screw or vane) that allures air, which is compressed into a storage container. Naturally, since the piston or rotary component needs to move consistently and smoothly for this to work, it generally needs to be lubricated.
In a lubricated air compressor, there is lubricating oil which will keep the piston or rotary element running smoothly without damaging the system. The lubricant also really helps to dissipate warmth and maintain air compression efficiency.
Oil-free of charge air compressors also use a piston or rotary element, however they bypass the lubrication problem by Water Lubricated Air Compressor coating the compression element with a pre-lubricating material like Teflon. Some oil-free compressors may also use water in place of oil for the lubricating and cooling process. These alternate materials protect the pump and allow the mechanism to go smoothly without the need for any oil-based or synthetic lubrication.