From the White Wolf Wiki, the most complete White Wolf reference

Spirit is one of the ten Arcana of Mage: The Awakening. It is the ruling Subtle Arcanum of the Primal Wild, paired with Life. Spirit magic can affect all aspects of the Shadow Realm; with it, a mage may perceive twilight spirits, command them to do her bidding, cross the Gauntlet between worlds and, like the Death Arcanum, affect the human soul.

Spirit magic cannot affect ghosts, and Death cannot affect spirits; they are different classes of being, despite both being made of ephemera. Indeed, spirits cannot usually be affected by any spell that does not make use of this Arcancum or Mind. Though both Spirit and Death may be used to affect souls, Spirit is limited to protecting or restoring them; Death grants greater control, though there are some affects it cannot duplicate.

Mage: The Awakening Arcana

Subtle Arcana: Prime · Fate · Mind · Spirit · Death Gross Arcana: Forces · Time · Space · Life · Matter