difference between regular user and system user (and groups)
 

What is the difference between creating a "regular" user and creating a "system" user on Linux?

For example:
and

Similarly it seems there are normal groups and system groups.

Doing an internet search and reading man pages does not give much information on the whole concept of system and regular user/group.

I don't know for sure, but I'm guessing it might do a few things like:
- use a lower ID number (most system users/groups start at something like 1000)
- avoid making /home directories for system users
- add the user to the least number of groups possible

Again, I'm just speculating though...