Rao's Theorem is a result in statistics that provides a way to improve the efficiency of estimators. It states that under certain conditions, the best unbiased estimator of a parameter can be obtained by combining the information from different sources. This is particularly useful when dealing with complex data sets. The theorem is named after C. R. Rao, an influential statistician who contributed significantly to the field. Rao's Theorem helps in deriving estimators that have the lowest possible variance, making them more reliable for statistical inference and decision-making.