Ezekiel 20:16

Because they rejected My ordinances, and as for My statutes, they did not walk in them; they even profaned My Sabbaths, for their heart continually went after their (worthless) idols.

In bible times, an idol was an image of something that people worshipped besides God.  Today, we don’t necessarily worship an image, but we focus on things other than God, to the point that God gets crowed of our lives.  An idol is meant to distract us from our actual purposes here on earth and, in most cases, leaves us unsatisfied and lesson our spiritual power—a challenge to clean out the idols and put God back as our primary focus.