A GHZ quantum circuit is a quantum computing system that includes 3 entangled qubits.
A Greenberger–Horne–Zeilinger state (GHZ state) is a certain type of entangled quantum state that involves at least three subsystems.
Demo in IBM Quantum Composer.
Great question. They actually are different. A GHZ only uses an H on the first qubit and then CNOT (controlled inverse) for the other two qubits, which ties them all together in an entangled state. At this point, any change to the first qubit will be reflected on the other two entangled qubits.
If the qubits, instead, each had their own H gate, they would not be entangled. Changes on any one of the qubits would not effect the others.