administrators: differences between "math a user" and "match all users" in a remote server

Hello,

 I have a question for the group and, yes, i've checked the documentation. The second option isn't there.

 When creating a local administrator for remote authentication i have two options: 

"Match a user on a remote server group": i got it working and i understood (it isn't that clear in the documentation) that my user must exists and be member of such group.

"Match all users in a remote server group": not sure of what this does.

 What does this option means? How do i use it?

 TIA.