What do churches that prohibit the use of icons think an idol is?

In the Orthodox and the Catholic Church icons and statues are permitted, and members of those churches look at such in much the same way they look at photographs of loved ones. We also talk to people depicted in certain icons, who we believe are in heaven, and we ask them to pray to God for us. (We ask the *people*, not the artistic renderings of those people.) Other churches that are opposed to icons and statues sometimes draw a comparison to idolatry. Usually this point makes reference to the commandment to not make idols: idols are a certain kind of image or likeness. So what's an idol, according to these churches? Presumably idols must include things like the Golden Calf. But they must exclude things like the cherubim mentioned in [Exodus 25:18-19](http://old.usccb.org/nab/bible/exodus/exodus25.htm) , since God would not command the construction of idols: > Make two cherubim of beaten gold for the two ends of the propitiatory, fastening them so that one cherub springs direct from each end. The question isn't "what practices of the Catholic Church involving images are disapproved of". The question is, these other churches must have some sort of definition of what counts as an idol. Is an idol something made of gold? Stone? Wood? Is it anything that depicts an animal, a human, or Jesus? Under what conditions do these churches consider something an idol?