The oldest survivor of this 6000 year old process is a copper frog cast in 3200 B.C. The most common technique used today is referred to as "Lost Wax Casting" or investment casting. This basic process is used in the making of jewelry, statues and industrial parts.
It begins with an original wax model of the desired piece. The model is then encapsulated in a molding material much like plaster with a small section attached known as a "sprue". The sprue will eventually create an opening in the mold. The mold with the model preserved inside is placed in an industrial oven which allows the wax to melt and burn away. Once burned away the hot mold is placed in a casting machine.
Under vacuum, molten metal is poured into the mold through the sprue opening to form an exact copy of the original wax model. The metal cools and once the mold is broken away it reveals the finished casting.