This lecture covers division rings, including the definition and properties of division rings, integral domains, and fields. It also discusses the relationship between division rings and domains, as well as the concept of ideals in a ring, including their intersection, sum, and product. Examples of ideals in Z are provided, along with the theorem that characterizes a commutative ring as a field. The lecture concludes with a detailed explanation of two-sided ideals and their significance in ring theory.