This new feature has been tested for a while, and now it is officially being rolled out. Chapters have become available for all channels. This is the feature that makes it very easy to divide video into different logical parts.
Chapters allow sectioning video into segments, and each of them has its description. They can be easily added by writing down timestamps in the description box. One thing worth noting here is that chapters will be added if your first timestamp begins at 00:00. Otherwise, timestamps are going to be just timestamps and nothing else.