One of my videos with chapters. See the description for an example of how to specify the chapters in the timeline.

 

For the past few weeks, you may have noticed something new on videos from some of your favorite YouTubers. 

If you hovered over the timeline of certain YouTuber’s videos, you’d see the timeline was split up into sections. If you hovered over a section, a brief description of what was contained in that timeframe would come up. Pretty nifty if you were looking for a specific topic of discussion within a longer video.