A file is considered locked when that flag is set. To batch unlock files (common when copying files from a CD, or when Dreamweaver has locked the files when using Check-in/Check-out), issue the command: chflags -R nouchg /path/to/folder
nochg means clear the "user immutable flag", which apparently is a fancy way of saying "locked". Use chg to set the file to locked.
In Unix, each file belongs to a single user and a single group. Unix file permissions control the ability to perform three actions: read from a file, write to a file, and execute a file. For a given file, the permissions allow or deny each of these three actions for the user who owns the file, the group the file belongs to, and everyone else. That's a total of nine permissions: read, write, and execute for owner, group, and other. In the text-based interface of Unix, the actions are traditionally abbreviated by the letters "r", "w", and "x." The file's owner and group are also displayed.
Unix only allows one user, or group, defined to have permissions set on a file. To get around that limitation, ACL's come to the rescue. OS X let's these two co-exist by first applying standard Unix permissions, and then applying any ACL's that may exist.
I have a .webarchive in my programming folder that describes this better. Also, check out the books from Safari Online.