That if you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved. (Romans 10:9-10, NIV)
When we use the term heart, we often use it to mean the seat of our emotions. However, in the Bible heart means the inner person (Daniel 4:16), not the physical inside, but it includes the mind, will (volition), and emotions. A saving faith includes not just believing facts about Christ, but a trust in Christ that saturates our will resulting in action and a dependence upon Christ that changes our desires and motives.
Confessing Christ by itself does not save us. This confession must be real. It must reflect the presence of Jesus in our hearts. On the other hand, a secret internal faith in Christ that remains hidden is not a saving faith. Once our lives are immersed in Christ what is on the inside cannot help from coming out.