* Spark Plugs: These are the components that create the spark to ignite the air/fuel mixture in the engine's cylinders. They are small, and there's one (or sometimes two) per cylinder.
* Coil Pack (or Ignition Coil): This is the part that provides the high voltage electricity needed to create the spark at the spark plugs. On some vehicles, including many 2000 Ford Expeditions, the coil pack is a single unit with multiple coils, one for each cylinder (or sometimes grouped for several cylinders). It receives lower voltage from the vehicle's electrical system and boosts it to the high voltage required for ignition.
Think of it like this: the coil pack is the power source, and the spark plugs are the delivery point. They both are crucial for the engine to run, but they are distinct parts.
