Series

The most important takeaway from this section is that series are just folders on your file system that live within the path of a library.

A series is just a folder

What defines a series?

A series is actually dependent on how its library is configured. A library can be configured to support 2 different patterns:

Collection based library: Takes the top most folder and collapses everything into it as a single series.
Series Based Library: Takes the bottom most folders as series, effectively being the opposite of a collection based library.

For more information on these patterns, please review the Library Configuration section of the documentation.