There are two primary differences between Frequentist and Bayesian statistics regarding estimators:

1. Frequentists consider a single estimator, $\theta$, to make all predictions, whereas Bayesian statisticians use all possible values of $\theta$ to make predictions.
2. Frequentists view the estimator $\theta$ as fixed and the dataset as variable, whereas Bayesian statisticians view the dataset as fixed and the estimator $\theta$ as a variable.