Normal commands move files into their proper places, and set their modes.
They may not alter any files except the ones that come entirely from the package they belong to. It is a post-installation command because it needs to be done after the normal command which installs the package's Info files. Most programs don't need any pre-installation commands, but we have the feature just in case it is needed. To classify the commands in the install rule into these three categories, insert category lines among them. A category line specifies the category for the commands that follow.