Which is a meaningless term unless you know Forgotten Realms mythology. And also false in other DnD worlds.
In the 2014 Players Handbook, the description of the Weave is − appropriately − contained in a sidebox. So it is easy to ignore if the DM has a different theory of magic in mind. But it is there as a default flavor. The Weave is true for every official D&D setting, including Dark Sun and Eberron, and Theros and Strixhaven. The Forgotten Realms setting calls it "the Weave", but other settings can refer to it by other names. But it is true in every official setting.
"
THE WEAVE OF MAGIC
The
worlds within the D&D multiverse are magical places. All existence is suffused with magical power, and potential energy lies untapped in every rock, stream, and living creature, and even in the air itself. Raw magic is the stuff of creation, the mute and mindless will of existence, permeating every bit of malter and present in every manifestation of energy throughout the multiverse.
Mortals cant directly shape this raw magic. Instead, they make use of a fabric of magic, a kind of interface between the will of a spellcaster and the stuff of raw magic. The spellcasters of the Forgotten Realms call it the Weave.
"
The Weave exists in all "worlds within the D&D multiverse". There is an ambient magic that "suffuses" all that exists. Existence itself is magical. Spellcasters make use of how this magic entangles things forming a "Weave".
This sentence annoys me, "mortals cant directly shape this raw magic", because creatures that have innate magic do shape it directly.
This weave is cosmic ambient magical potential. And Arcane and Divine use different methods to access it.
The description of the Weave ignores Psionic and Primal, as well as superhuman Martial.
Tashas mentions the Psionic magic is innate "within" and personal, and its source is the "mind", "the minds power", "mental force", and so on. Notably, for the Psi Warrior, the "various Psionic powers" are class features and arent spells. Psionic is always magic, but not necessarily spellcasting.
In any case, the example of 5e Psionic that utilizes the mind of the soul, suggests the D&D tradition that distinguishes a personal weave that is distinct from the cosmic ambient weave.
Inferrably, there is a cosmic weave versus a personal soul. Both can be sources of magical effects.