Is a shell setting that you can use to show and set current default permissions that work as a substraction to the default permissions 777 on a directory and 666 on a file.
Default permissions on directories are 777
Default permissions on files are 666
umask 022 # will set default permissions on files to 644 (755 on directories)
umask 027 # will set default permissions on directories to 750 (640 on files)