Duplicate section can be used if you want to add a similar section in your pattern.
For Example: If you want to add one more column in between your Featured Content Duplicate section can be used, as it will create a similar section and you can edit the content accordingly.
Duplicate section is a very easy step to add on particular sections in your pattern.
Select the column via ListView/Footer Interface, then click on three dots and select Duplicate then change the content accordingly