[benkahuna]

This is the ultimate unanswered question in neuroscience. It's called the binding principle.
No one knows how our neurobiological processes produce consciousness. It's a complete mystery.

There's an incredible amount that is understood in neuroscience, but consciousness and how it arises is a mystery in many ways.
Take a neuroanatomy course and you'll be shocked what they've figured out (and sometimes how they figured it out).

Thought tends to be classified as an emergent property of our neurobiological processes.

Basically when you move up a level of organization, you have new rules that govern the behavior of that larger system not based strictly on the rules of the less complex lower system.

You could take as levels of organization:

quark, atom, molecule, organelle, cell, tissue, organ, organ system, organism.

Beyond the concept of emergent property, it's just this funky, ephemeral, largely unclassifiable event. It's completely different from any other occurance in the
world of which we're aware. Computers crunch numbers and follow orders (sometimes in strangely efficient ways), but what they do and what the brain does are two completely different things. No computer has come close to passing the Turing Test.