'Idol' in the Bible

Therefore, concerning the eating of food sacrificed to idols, we know that "an idol [is] nothing in the world" and that "[there is] no God except one."

But this knowledge [is] not in everyone. But some, being accustomed until now to the idol, eat [this food] as food sacrificed to idols, and their conscience, [because it] is weak, is defiled.

Therefore, what am I saying? That food sacrificed to idols is anything, or that an idol is anything?