This lecture covers the concept of topological sort in directed graphs, explaining how to determine if a graph is acyclic using Depth-First Search (DFS). It also delves into Strongly Connected Components (SCC) and presents a magic algorithm to find SCCs in a graph. Additionally, the lecture discusses the component graph of a digraph and its properties. The flow networks and their applications are explored, showcasing how to maximize flow between different nodes. The summary emphasizes the importance of graphs, DFS, topological sort, SCCs, and flow networks.