Intercession is the act of prayer to God on behalf of others. Romans 8:26-27 explains what intercession is.
26 Also, the Spirit helps us. We are very weak, but the Spirit helps us with our weakness. We don’t know how to pray as we should, but the Spirit himself speaks to God for us. He begs God for us, speaking to him with feelings too deep for words.
27 God already knows our deepest thoughts. And he understands what the Spirit is saying, because the Spirit speaks for his people in the way that agrees with what God wants.