The Pauli-Z gate is a fundamental quantum gate used in quantum computing. It is a single-qubit gate that applies a phase flip to the qubit's state. Specifically, it changes the sign of the amplitude of the |1⟩ state while leaving the |0⟩ state unchanged. This means that if a qubit is in the state |1⟩, applying the Pauli-Z gate will transform it to -|1⟩. In the context of quantum mechanics, the Pauli-Z gate is part of the Pauli gates, which also include the Pauli-X and Pauli-Y gates. These gates are essential for manipulating qubit states and are widely used in quantum algorithms and error correction. The Pauli-Z gate is represented by the matrix [[1, 0], [0, -1]], which succinctly captures its effect on qubit states.