
Basis States:
We represent the standard quantum states as column vectors:

Applying Pauli Matrices on ∣0⟩and ∣1⟩:
Pauli-X

It flips the bit — just like NOT gate.
Pauli-Y

It flips the bit and adds a phase shift.
Pauli-Z

It leaves |0⟩ unchanged and adds a phase flip to ∣1⟩|1⟩∣1⟩.