No need to get confused, well it just means that the directory has extra acl permission. We use acl to give individual permission for users or groups on any directory.
I have a directory deepak inside my root home directory
# ls -l | grep deepak drwxrwxr-x 2 deepak deepak 4096 Sep 24 16:14 deepak
Now I want to give a different user test additional rwx full permission on this directory so what am I suppose to do?
One option is that I will have to add test user to group owner of deepak directory but I really don't want to do that then in those case setfacl plays its role
# setfacl -m u:test:rwx /root/deepak # ls -l | grep deepak drwxrwxr-x+ 2 root root 4096 Sep 24 16:14 deepak
# getfacl /root/deepak # file: root/deepak/ # owner: root # group: root user::rwx user:test:rwx group::r-x mask::rwx other::r-x
So as you can see all the acl details using the above command. For more detailed help and examples on setfacl follow the below link