Intercession is a prayer of petition which leads us to pray as Jesus did. He is the one intercessor with the Father on behalf of all men, especially sinners. He is "able for all time to save those who draw near to God through him, since he always lives to make intercession for them." The Holy Spirit "himself intercedes for us . . . And intercedes for the saints according to the will of God."
Source: Catechism of the Catholic Church (Vatican.va)