Greenberger–Horne–Zeilinger state
It is an entangled state produced by the following circuit:
This circuit produces the following state: $$\begin{aligned}
\ket{000} &\xrightarrow{H \otimes I \otimes I} \frac{1}{\sqrt 2}(\ket{000} + \ket{100}) \newline
&\xrightarrow{CNOT_{21}} \frac{1}{\sqrt 2}(\ket{000} + \ket{110}) \newline
&\xrightarrow{CNOT_{20}} \frac{1}{\sqrt 2}(\ket{000} + \ket{111}).
\end{aligned}$$
If we measure it, we find that all the qubits are $0$ with probability $1/2$ or all $1$ with probability $1/2$. 1