Vedanta means the end of the Veda or final knowledge and is the last of the 6 systems of Indian Philosophy (Yoga is the 4th). We also know these systems as the Vedanga or subordinate limbs (to the core books of the Veda) and as the Darshana.
The core text of Vedanta is the Brahma Sutra of Bādarāyaṇa. The Upanishads and the Bhagavad Gita are also generally considered Vedantic texts.
But like any older philosophy, it has drifted into mind and concepts and then to distinct schools of interpretation. There are three primary schools of Vedanta with many sub-branches.
The one you’ve most likely heard of is Advaita Vedānta, an approach that emphasizes the non-dual nature of reality. In this outlook, the jiva or individual soul is Brahman. There is only one.
Modern neo-advaita is derived from this branch, but could be said to be a simplified version with various interpretations.
A second branch is Dvaita Vedānta that takes a dualistic perspective. The jiva is distinct from Brahman.
And the third is Bhedābheda Vedānta. Bhedābheda means “difference and non-difference.” From this perspective, jiva is Both different and non-different from Brahman.
There are various ways we could argue each position based on our experience or philosophy. However, I’d suggest this is a misunderstanding of the intent of Vedanta. Brahman can’t really be known except by being it. It is beyond the range of consciousness and yet immerses all.
If we apply the perspective of stages, we can see these perspectives each come out of different steps of unfolding.
Dwaita is a key aspect of Self Realization. In that stage, we wake up to ourselves as Atman, the universal Self or infinite Being. But that Self is distinct from our personal self we had previously identified with. And distinct from the world. This is inherently a dualistic stage, although some argue otherwise. For example, they may say the world is an illusion and only the Self is real, so there is just one thing. And the Upanishads tell us the Self is Brahman so there’s just one here. (Ironically “Self is Brahman” (Ayam Atma Brahma), a mahavakya, describes a recognition not a philosophical position.)
Advaita is a key aspect of the Unity stage when the Self within is recognized to underlie the world. Subject and object come together in one wholeness. This usually develops in stages as we live life and recognize “That is also mySelf” with each layer of experience, memory, and so forth.
Only in the Brahman stage does Brahman come to know Itself. Only Brahman knows Brahman. As the stage matures, it becomes inclusive of all prior stages and all layers of experience. Even the subtle dualities of Unity fall away into Totality.
We see the world as non-existent (not illusory – that’s earlier) and yet here it is simultaneously. Brahman stage is the great integrator, the grand inclusivity even of apparent opposites.
This is when you come to Bhedābheda – differences and non-differences. It is both oneness and diversity, real and non-real, complete and empty. It is the flattening of all paradoxes.
This is not a philosophical position, but a direct way of knowing reality.
There is a related set of terms that can also illustrate the distinction. VivartaVada means speaking of modification. It is the Advaita way of describing causation, saying modifications or change are merely illusion and are not real. Only Brahman is real. They attribute this to Shankara, however, as I’ve written elsewhere, Shankara’s view was far more inclusive.
The other term is AtitaVada, speaking of the beyond. This points to Bhedābheda.
None of these positions are “better” than another. They simply describe the unfolding.
I would also caution you not to adopt a philosophy that doesn’t relate to your reality. This is delusional and creates inner divisions. It’s useful to see where we’re going, but acting like we’re in Aukland when we’re in Toledo will cause trouble. Be aware of the road ahead, but keep it real.