Actually in D&D it'ss a major distiction. It's the whole point and basis of having seperate caster in D&D..
Clerics get their powers from the top dogs of the cosmos who control the portfolios: the gods.
Druids get their powers from the divinity of nature itself or the many lingering energies of nature gods, spirits and elementals.
Warlocks are the the next rung down who get their powers from powerful beings who either lack divinity, portfolios, or decide not to share their power.
Wizards are next in the source order and tap into the basic building blocks of magic that isn't channeled through powerful beings.
Bards follow them by commiting to a bastardie version of wizard magic via the magic of song. It's wiggly enough to snag from some divinity and nature magic.
Sorcerers are last as they have magic in their blood. Their source is weakest as it is diluted in mortal blood, often comes from nondivine beings, and might not come from a living entity at all.
- Gods
- Nature
- Powerful immortals
- The Code
- The worse code
- Monsters and the elements
D&D puts gods, devils, and dragon on different tiers.