If you run ls on a file or folder in OS X...

ls -la /dir/to/some_file_or_folder

You may see a permission entry like this:

-rwxr--r--@  1 john  admins   548 Oct 29 15:58 filename.plist

The at sign (@) means that the file has "extended attributes". Extended attributes are basically some metadata that OS X and OS X apps can tack on to a file.

To view the extended attributes of a file, type:

xattr -l ./filename.ext