Idolatry is the worship of idols. This does not just mean the worship of images made out of stone, wood, or precious metals. An idol is anything that is more important to you than God. Idolaters are those who practice idolatry and worship something other than the true God. Idolatry is the lack of acknowledgment of the rightful position of God in your life.
One of the first commandments given by God concerned idolatry:
Turn ye not unto idols, nor make to yourselves molten gods: I am the Lord your God. (Leviticus 19:4)
Ye shall make you no idols nor graven image, neither rear you up a standing image, neither shall ye set up any image of stone in your land, to bow down unto it: for I am the Lord your God. (Leviticus 26:1)
The gods of heathen nations are called idols:
For all the gods of the nations are idols: but the Lord made the heavens. (Psalms 96:5)
You will be confounded [or confused] if you serve idols:
Confounded be all they that serve graven images, that boast themselves of idols... (Psalms 97:7)
The idols of the heathen are the work of man. They have no power or true spiritual significance:
The idols of the heathen are silver and gold, the work of men's hands. They have mouths, but they speak not; eyes have they, but they see not; They have ears, but they hear not; neither is there any breath in their mouths. They that make them are like unto them: so is every one that trusteth in them. (Psalms 135:15-18) (See also Psalms 115:4-8).
A Christian cannot worship idols:
And what agreement hath the temple of God with idols? (II Corinthians 6:16)
You are not to even keep company with idolaters:
But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one go not to eat. (I Corinthians 5:11)
You are warned to keep yourself from idols:
Little children, keep yourselves from idols. (I John 5:21)
Idolaters will not be part of the Kingdom of God:
Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived...neither idolaters...shall inherit the kingdom of God. (I Corinthians 6:9-10)
The Bible reveals the destination of idolaters:
But the fearful, and unbelieving, and the abominable and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone; which is the second death. (Revelation 21:8)
For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie. (Revelation 22:15)
The Bible calls covetousness a form of idolatry. Covetousness is wanting something with an intense and wrong desire. You are to mortify and destroy covetousness:
Mortify therefore your members which are upon the earth: fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry. (Colossians 3:5)
You may have been an idolater in times past, but believers are no longer to continue with this practice:
That he no longer should live the rest of his time in the flesh to the lusts of men, but to the will of God. For the time past of our life may suffice us to have wrought the will of the Gentiles, when we walked in lasciviousness, lusts, excess of wine, revellings, banquetings, and abominable idolatries... (I Peter 4:2-3)
For they themselves shew of us what manner of entering in we had unto you, and how ye turned to God from idols to serve the living and true God. (I Thessalonians 1:9)