Eternal procession of the Holy Spirit
The eternal procession of the Holy Spirit is a concept in Christian theology, affirmed in the Nicene creed of 325, that describes the relationship of the Holy Spirit to the other persons of the Trinity. It is related to the doctrine of the eternal generation of the Son; but in Christian theology procession (or spiration) is viewed as being mysteriously different from generation in order to distinguish the Holy Spirit from the Son.
When the Paraclete comes, whom I will send to you from the Father—the Spirit of truth Who goes out from the Father—He will testify about me.
In Western Christianity, the Holy Spirit is believed to proceed from the Father and the Son. This is in contrast to the Eastern churches, which believe that the Holy Spirit proceeds only from the Father. This issue led to the filioque controversy and was a large question in the East-West schism.