When you intercede, you try to help people work out their differences or achieve something, like when you intercede on your friend's behalf to encourage your boss to hire him, or when feuding friends ask you to intercede, guiding them to sort out their differences.
The verb intercede comes from the Latin root words inter, meaning "between," and cedere, meaning "go." Acting as a go-between is exactly what you do when you intercede. Maybe you are the peacemaker, or you play matchmaker, or you just bring people to work out their problems. Sometimes people pray that God will intercede in their lives, meaning bring change that improves a situation.