There are several types. I think the most common ones go in a one of the engine block's "freeze plugs". To install, you need to remove one of the freeze plugs which isn't usually that hard but you need to drain down your cooling system which is a pain. It's just a round heating element with a cord that you usually run out thru the grill so it's easy to plug in. There are others that install in a rad hose (easier to install) or attach to the oil pan. They are a necessity especially on diesel engines in cold areas and they help get you heat faster also. They need to be fairly high wattage to do any good. Don't remember for ure but probably 1500 watts or above. Another option is a "battery warmer" that heats your battery to give more amps at startup but does nothing for your comfort. Anyway, if the car has some form of block heater, there will be a standard looking 3 prong plug somewhere. Good luck

bl