Idolatry means the worship of images as if they were gods. Many religions prohibit idolatry, some even to the extent of forbidding any representational objects in houses of worship.
Idol sits at the head of the word idolatry. If you worship — or even just look up to — a person or a thing, you are said to idolize them. For some modern idolaters, money is their idol, while for others it is celebrities, and for still others their jobs.