Asymptotic Theory is a branch of statistics that focuses on the behavior of estimators and test statistics as the sample size approaches infinity. It helps statisticians understand how certain methods perform in large samples, providing insights into their efficiency and consistency. This theory often involves concepts like convergence in distribution and asymptotic normality, which describe how the distribution of estimators behaves under large sample conditions. By using asymptotic results, researchers can simplify complex problems and make approximations that are useful for practical applications in fields such as econometrics and biostatistics.