There is quite a bit of difference between a statue and an idol, and it has to do with mentality.
The Catholic Church allows statuary of Jesus, His Mother Mary, and the saints to be placed in Churches and in homes. The understanding is that Catholics venerate the saint in heaven by honoring their picture. Catholics do not worship statues. They know they are only made out of wood, plaster, or marble.
Just like someone has a picture of deceased relative in their wallet, so many Catholics have a picture of a certain saint. We praise God through the five senses, and sight (through which we look upon and then contemplate religious images) is one of these senses.
Idols, such as the golden calf constructed by the Israelites, were worshiped as gods and divine powers were attributed to them. In no way are statues or icons given this status. However, as a spiritual tool and sacramental, the faithful can think of the person in heaven as a visual reminder when they are praying.
In the ninth century in the Eastern Church, there was a great battle about whether to keep icons in churches, but it was eventually decided that devotional items would remain in churches. That decision is commemorated to this day in a feat known as the Triumph over Iconoclasm. In the sixteenth century, Protestants who hearkened to the Book of Exodus and admonishments over the Israelites’ golden calf rid all of their churches of any statuary.
Even the corpus was taken off the cross. During the Council of Trent and the Counter-reformation period, the Church continued to teach that statues were perfectly acceptable in homes and churches, reminding us that Catholics do not worship the art but revere the saint in heaven through the art.
