The permissions in the bit patterns you gave in your question are broken down as follows:
The bits are broken down thusly:
- rw- --- ---
^-- denotes a directory ^-- user bits ^-- group bits ^-- other bits
Each pack of bits (user, group, other) contain 3 values.
- r = read
- w = write
- x = executable
So a grouping of
-rw-rw-r-- means it's a file with user & group read/write permissions, and other users have only read access. A grouping of
drwxr-x-r-x means that it's a directory, and that the owner/user has read/write/execute permissions on the directory, and the group and others have only read and execute permissions.
The owner of a file/directory is the username listed in the 3rd column of
ls -l output. The group that's associated to a file/directory is the 4th column, again a group called
root. The Set of other users is basically anyone that doesn't fall into either of the first two categories (i.e. not the user root, not the group root).
-rw-r--r-- 1 root root 1749 Apr 14 2005 b
drwxr-xr-x 2 root root 4096 Dec 19 22:48 bin
drwxr-xr-x 2 root root 4096 Apr 10 2005 Desktop
Note on permissions bits
For simplicity sake I'm ignoring that there are in fact more potential bits than the standard r, w, and x. See the chmod wikipedia page for more details.