Magic fuals magic items and "spells" and (magic) items and spells absorb(or mabye disperse) magic. Magic items and spells are willed to activate and deactivate (probably by "channelling" magic throuh them).
In addition to items and spells Deku Scrubs, Gorons, and Zoras endowed with fairy magic gain (or perhaps have awakened in them) special biological abilities which vary by species, such as the ability to shoot bubbles or grow metal spikes.