This video is about doing a wall clock time investigation of ASP.NET scenarios using the PerfView tool. It is best to watch the video using one of the high quality links on the right so the text is readable. If you have not already watched the video on wall clock time basics, you should do that first (as well as the even more fundamental videos it will refer you to). You may also be interested in the video on wall clock time for parallel/async programs.
As explained video on the basics wall clock time investigations, the key to doing such an investigation is focusing in on a 'critical path' of interest. For ASP.NET scenarios the most obvious such path is the time it takes to respond to any particular request. PerfView supports this idea by creating the 'ASP.NET Thread Time view', by identifying the snippets of time on individual threads that represent work to respond to the request, and associating this cost to a particular request (and further grouping requests by URL. This allows you to quickly segregate 'uninteresting' time where threads are simply waiting for work from the 'important' time when it is on the critical path to respond to a request. The result that it is very straightforward to drill into performance problems on any particular request.
There is a companion perfView blog entries that you may be interested in. In particular there is a ZIP file of source code and data used in this tutorial, so that you can explore this data and 'follow along' yourself with what was done in this video. To use the zip file simply open it, and drag the directory inside to your desktop (or other location). The file contains an HelloWorld.ASPX file (the source code, just view in notepad) as well as the AspNetHelloWorld.ETL.ZIP file (The data file used in this video) You don't need to unzip this file, simply open it in PerfView.
You may be interested in the entire PerfView Tutorial video series,