MSE stands for Mean Squared Error. It is a measure of the performance of an estimate or prediction, equal to the mean squared difference between the observed values and the estimated / predicted values.
MSE stands for Mean Squared Error. It is a measure of the performance of an estimate or prediction, equal to the mean squared difference between the observed values and the estimated / predicted values. For predictions $\hat{y}_1, \dots, \hat{y}_N$ and corresponding actuals $y_1, \dots, y_N$, the MSE is defined as
$$\text{MSE} := \frac{1}{N}\sum_{i=1}^N(\hat{y}_i-y_i)^2.$$
Alternatives to the MSE as a point forecast accuracy measure include the mase, the mae and the mape.