Single qubit Hadamard gate transforms $$\mid 0\rangle$$ state to $$|+\rangle=\frac{\mid 0\rangle + \mid 1\rangle}{\sqrt{2}}$$ state and $$\mid 1\rangle$$ state to $$|-\rangle=\frac{\mid 0\rangle - \mid 1\rangle} {\sqrt{2}}$$ state and so, in matrix form, can be written as $$H = |+\rangle\langle 0|+|-\rangle\langle 1|= \frac{1}{\sqrt{2}}\begin{pmatrix}1&1 \\\ 1&-1\end{pmatrix}$$. taken from https://www.kisspng.com/png-quantum-logic-gate-hadamard-matrix-hadamard-transf-4947412/
The $$n$$-qubit Hadamard gate can then be written as $$H^{\otimes n} = H\otimes H^{\otimes \left(n-1\right)}$$ and is $$n$$ individual Hadamard gates acting on $$n$$ different qubits.