These are the spheres of priestly magic used in Talents of Faerun. They are loosely based on AD&D 2nd Edition categories but have been significantly streamlined for better balance in the BG/IWD context.
The spheres used by core classes are:
Speciality priests added or edited by ToF always get access to All, Divine, and Protection; virtually all also get Healing. Hopefully these spheres contain all the 'must-have' cleric spells, so that no speciality priest is unusable. Typically, one or two other cleric spheres are lost and replaced by druid spheres and/or wizard spells.
Spells added by other mods are categorised automatically. Those usable by clerics and druids are added to All. Those usable by clerics but not druids are added to Divine. Those usable by druids but not clerics are added to a new sphere, Nature, which is empty if you install ToF on an unmodded game; druids, rangers and shamans can use spells from the Nature sphere.
Spheres may be customized by editing the files in dw_talents/shared/sphere using a text editor.