What the purpose of a lightning rod?

A lighting rod is a metallic rod, which is put in place to provide a route for electric charge to travel to the ground. It is placed at the top of a high building, and connected to a wire which runs down the side of said building and connects to a ground rod, which is placed underground. The reason why these are put in place is to avoid tall buildings being struck by lightning, as this could cause high temperatures in the building or even start a fire.