What are the groups 'users' and 'other' for?

There is a proprietary document about system hardening/security standard stating that group users, nogroup, other, and some other groups should not contain any user except system administrators. I've found an explanation about nogroup group [here](https://unix.stackexchange.com/questions/22520/what-is-nogroup-groups-purpose) . What about the users and other groups and what are they for? Why regular (non-administrator) users should not be member of these groups? Distro is, RHEL (Red Hat Enterprise Linux)