Aschbacher's theorem is a significant result in the field of group theory, particularly concerning the classification of finite simple groups. It provides a systematic way to understand the structure of these groups by breaking them down into smaller, more manageable pieces. The theorem identifies specific types of subgroups, known as normal subgroups, that can be used to analyze the larger group. The theorem is named after Michael Aschbacher, who proved it in the 1980s. It plays a crucial role in the broader context of the Classification of Finite Simple Groups, which is a monumental achievement in mathematics that categorizes all finite simple groups into distinct families.