Depending on your tradition, the Nicene Creed may or may not say that the Holy Spirit proceeds from the Son as well as from the Father:
(Greek) τὸ ἐκ τοῦ πατρὸς ἐκπορευόμενον - who from the Father proceeds
(Latin) qui ex Patre Filioque procedit - who from the Father and the Son proceeds
This has been a point of contention between the Orthodox and Western churches, the latter category including both Catholics and Protestants, for at least a thousand years, contributing to the Great Schism. I have read about the history of "filioque" but I have basically no idea what the theological difference is meant to be. I understand that there is some doubt about whether "ἐκπορευόμενον" means the same thing as "procedit", so both versions could be right (and apparently we all agree it would be wrong to insert "and the Son" into the Greek) but I don't see what either version of "proceeding" is meant to imply about the nature of the Trinity.
If the Spirit proceeds from the Father and the Son, or from the Father alone, what does that actually mean for our understanding of God?