An idol is anything you place above God. More specifically, anything you love more than God.
It’s the thing you dream about, fixate on, want to have. It’s the thing that captivates you.
The movie, Raiders of the Lost Ark, depicted this perfectly.
Agents of Nazi Germany are attempting to locate and control the biblical ark of the covenant. In the movie, the ark represents a direct connection to God and thus power over others. That’s the first idol – the insatiable lust for power – and it is personified by the German character, Major Arnold Toht.