im a little confused about these 2. i understand them and how they work. but the topological ordering with dfs that we learned on tuesday , is different from the Kosaraju algo were using thursday right?  or does Kosaraju use topological sorting? i was thinking that the first dfs pass of Kosaraju uses topological sorting and then the 2nd dfs pass finds the scc's of the graph.

Topological sorting and Kosaraju's algorithm operate on different sorts of graphs. Topological sorting works only on DAGs. Strongly connected components don't exist in DAGs. To have a strongly connected component you need loops in the graph, which violates the DAG condition. It's best to think of the two algorithms as different. 

On the other hand, once one runs Kosaraju's algorithm, if one thinks of each SCC as a node in what Roughgarden called a meta-graph, the resulting meta-graph is a DAG. So in that sense they are related. But Kosaraju's algorithm does not find labels for the meta-graph as a topological sort would do. 

I know that may all sound confusing. So the best thing is not to try to relate the two algorithms. Just understand each one on its own terms.

Just for clarification:

Are you saying Kosaraju's algorithm did not label the graph at all or that it does so in a different method from a topological sort?

According to the video, I thought it was the latter.

Thanks