Meaning of ContentSet parameter in RHSM-API

Greetings

I would like to use the RHSM-API (listed here https://access.redhat.com/management/api/rhsm), but I can't find anywhere the explanation what does the ContentSet parameter include or what are some valid options that could be used here.

It is used, for example, to get all the errata for the specified content set and arch (API - /errata/cset/{ContentSet}/arch/{Arch}).

I would be very thankful if someone could point me to the right direction.