Permissions provide security to keep one user
from modifying or viewing another user's files. They are important
because Mac OS X was designed to be used by more than one
person.
If an application's permissions are not set
properly, the application may not launch, it may not be able to
save files, it may not be able to open specific types of files, and
files created by the application may have problems.
The Verify Disk Permissions and Repair Disk
Permissions buttons in Disk Utility's First Aid pane, the Finder
Info window, and the Terminal application for file system view of
file permissions.
