Unix permission other class [migrated]

Say I’m having the following configuration on a unix system:

usr : grp (User usr is of group grp). In addition I have group gurus.

And I’m running ls -l and get the following output:

-r--rw--w- 1 usr gurus  

Does usr have a write permission of this file? i.e does the ‘other’ class means “the whole world” or “not an owner nor a group member”?”