Magic
First let's talk about Psi or Psy. This is a skill which makes it possible for the thinking mind to manipulate the physical world directly (without the mediation of the Psi-user's body). It's similar to DnD's Psionics.
Three schools exist, one for Wizards, one for Martial-artist, and one for everyone else. Some classes get it by default but available to learn to the others too.
Psi gives the character certain spells, like Waking (one can set his/her inner clock to wake him/her in a specified time of the day), Relieving pain (restoring Pain Points basically), Boosting abilities (the primary ones), Telepathy, Telekinesis, Raising/reduce body heat, etc.
It helps with Magic Resistance, shielding the Mental and Astral Body or in reverse destroy someone else's.
Wizards use this to recharge their Mana pool from the Web of Mana which embraces the whole planet. Some places it is woven thicker some places has holes in it. Of course every KM knows such places are the best for adventures if a Wizard is in the party.
Martial-artists gain powers similar to DnD ki and other stuff, like Levitation, Time Slow and other crap that makes the overpowered.

Clerical magic is sacral magic. There are 4 spheres: Life, Death, Soul, Nature. Every god has influence over some or even all of them, and they grant spells belonging to these spheres to their Clerics and Paladins. The Clerics and Paladins have to live their life along the teachings of their religion, they have to sacrifice to their gods otherwise they lose their powers.

Magic of Bards, Witches and Witchmasters are profane, empirical magic, they are merely users, appliers. Their spells differ to each other and they have different methods to recharge their Mana pool.
For example Bards gain their Mana from the stars they have to sound the vocal harmony of them (don't ask). Of course for Bards the KM will tell stories when it's raining all night every day. Witchmasters have to drink a Potion of Power to recharge the Mana. They won't find any ingredients for these potions during their adventures that's for sure.
Firemages gain their power from a fire god via fires. Basically. Most of their spells are destructive with a few exception, they can open teleportation gates to fires far away or summon entities from the Elemental Plane of Fire (because a good fantasy always need such Planes).

About the magic of the Wizards (mosaic-magic) I talked briefly in a previous post and that's enough. They can do lots of stuffs with material, time, space, signs, Astral, Mental, summonings, Necromancy and the combinations of all of the above. They are OP as fuck.
Especially if they start creating magic items. Some of these of course can be made by profane magic users too.