Idolatry in Christianity means worshiping something or someone other than God. When we go to church or pray, we are talking to God who we believe is the one who created everything and who loves us very much. Idolatry is a way of showing love or respect to things that are not God, like statues or pictures of famous people or animals.
God tells us in the Bible that He is the only one worthy of our worship, and that means we should only pray to Him and think about Him when we want to show our love or ask for help. When we worship other things, it can make God feel sad because He wants to be the most important thing in our lives.
Being a Christian means we follow the teachings of Jesus, who showed us how to love and serve God. Jesus taught us that the most important commandment is to love God with all our heart, soul, mind, and strength. If we love God this much, we won't want to worship anything else.
So, in short, idolatry in Christianity means we shouldn't worship things other than God because He is the only one who deserves our love and worship.