u => user, g => group, o => or others, a => all
# They are equivalent permissions:chmod o+rwx myfilechmod 007 myfile
In addition to the basic permissions, there are three other permissions that are used in certain situations.
SUID => Set User ID (for user):
chmod u+s my_file
SGID => Set Group ID (for group):
chmod g+s my_file
Sticky => for everyone:
chmod o+t my_file
SUID => When this is set on a file, script or executable, it means run that file or application with the permission of the user owner. Typically, this is run against a root file. It looks like the following:
Sticky => When it is set, only that user owner will be able to delete that file.