Automake knows that different types of files should be treated differently.
For the build infrastructure, these are the simplest files. Just install them without change.
Public header files.
Usually built from a number of sources. Can be stripped. Should be installed as executables.
Installed as executables. Can have their name transformed (the --program-transorm-name flag to configure). Cannot be stripped (so they are different from programs).
Installed into the appropriate directories. For example, automake knows that bar.3n goes in section 3 (despite the trailing n). For info documents, it knows to run install-info on the results to put them into the directory, and so forth.
Specifies that the files are static or shared libraries, possibly created with libtool (not covered in this tutorial).