The Source is a metaphysical concept created by writer/artist Jack Kirby for his Fourth World series of comic books. It first appeared in New Gods #1 (February 1971).
It is the source of all that exists. Mostly associated with the New Gods, the Source was the supposed origin of the Godwave that is believed to have been responsible for creating and empowering the "Gods" of the DC Universe with their divine abilities. It also seems to be partially responsible for the ability of DC residents to develop super-powers, especially those which defy physics. Lying at the edge of the known universe in the Promethean Galaxy is the Source Wall, which protects the Source, and traps all those who attempt to pass beyond it.
Powers and Stats
Tier: Likely 1-A
Name: The Source
Origin: DC Comics
Age: Older than the DC Multiverse / Time
Classification: God, Abstract Being, Supreme New God, Aspect of the Overmonitor
Attack Potency: Likely Outerverse level (Placed in the same level of existence as The Void itself in DC's Multiversity Map. Described as spawning directly from The Void, as a "Boundless and Timeless" place)
Lifting Strength: Likely Irrelevant
Striking Strength: Likely Outerversal
Durability: Likely Outerverse level
Range: Likely Outerversal
Standard Equipment: Inapplicable
Basically, The Source in general is treated as an embodiment of Nirvana, a formless transcendent calm and completeness beyond all spatial dimensions and possible divisions.
In Death of the New Gods, it was treated as a physical being that had been divided into parts, was a stand-in for the writer Jim Starlin's Marvel creation The In-Betweener, and had a completely different humanised malevolent personality.