PIX timing captures record information about when each piece of work was carried out by the CPU and GPU. This data is gathered in realtime while the game is running, and with minimal overhead, so you can see things like how work is distributed across CPU cores, the latency between graphics work being submitted by the CPU and executed by the GPU, and how GPU rendering workloads are overlapping with async compute.
Timing captures work best when the game has been instrumented using PIX events. If you are running a recent Insiders build of Windows 10 Creators Update, aka RS2, you can also use the SetThreadDescription API to label your threads.
Timing captures can optionally also capture callstack information. This data can be useful, but enabling it increases overhead of the data collection: