I have come across many people in my life who believe that Catholics worship the saints, or worship medals.
None of these are true.
The definition of idolatry is "the worship of idols." This practice is against the Ten Commandments, so it is sinful in any Christian denomination. Some non-Catholics, particularly Protestants, accuse Catholics of worshiping saints or their medals and relics.
Saints are, in general, souls in heaven. Canonized saints are holy persons that are in heaven with God, that the Pope decrees to be a person of good example for all Christians, and even non-Christians. Often, these saints have gifts from God. For example, Saint Elizabeth of Portugal's body remained free of decay after death, looking as if she was merely sleeping. She was examined by multiple medical professionals. Many other saints have been found like this as well. Other saints, such as St. Padre Pio of Pietrelcina, received gifts such as the ability to read souls, bilocation, stigmata (the wounds on his hands and feet identical to the wounds of Jesus when He was crucified), and healing.
We do not worship these saints, no matter how holy they are, because only God is deserving of worship. We do not worship their saint medals either. These saints are models for us, to inspire us to be better Christians, and better humans in general.
We may pray and ask the saints to intercede for us, but we don't pray to them. For example, we could pray "Saint Pio, pray for my recovery." We ask the saints to pray to God on our behalf.
We do not worship their medals either. They serve as a reminder of the saints, similar to how a photograph reminds you of a special someone. If you have a photo of your mom, you don't worship her, or the photo. It just reminds you of her.