What was Auguste Comte best known for that relates to sociology?
Auguste Comte was, in some ways, the founder of the whole discipline of sociology. It was he who made up the term "sociology" and it was he who pioneered what he saw as the objective study of society.
Comte felt that people who had studied society before him had generally done so from a critical point of view. They had been more interested in criticizing society than in studying it. Because of this, he became interested in studying the whole of society and in figuring out the functions of various aspects of society that other people thought were simply bad. He tried to explain how those aspects of society functioned as part of the whole rather than simply arguing that those aspects were dysfunctional. In doing so, he helped to start a new discipline in which scholars tried to study society in an objective way.
Comte, then, is best known for being one of the fathers of modern sociology.