As per Central tendency ( x̅ - E(x̅))/ Std(x̅)central limit theorem $(\bar x- E(\bar x))/ \operatorname{Std}(\bar x)$ follows standard normal distribution with mean 0 and standard deviation of 1.
iI.e. ( x̅ - E(x̅))/ Std(x̅)$(\bar x- E(\bar x))/ \operatorname{Std}(\bar x)$ follows N(0,1)$N(0,1)$ or equivalently x̅$\bar x$ follows Normal with mean E(x̅)$E(\bar x)$ and variance var(x̅)$\operatorname{var}(\bar x)$.
Note that E(x̅) = θ$E(\bar x) = \theta$ and as Var(x) = θ$\operatorname{Var}(x) = \theta$ for a Poisson distribution, Var(x̅) = θ/n$\operatorname{Var}(\bar x) = \theta/n$ which basically mean x̅$\bar x$ follows normal distribution with mean θ$\theta$ and variance θ/n$\theta/n$.
Hope this clarifies your answer