This uses the param package and so it has access to the help parameters
which give a comprehensive message describing the usage of the program and
the parameters you can give. The -help parameter on its own will print the
standard parameters that the program can accept but you can also give
parameters to show both more or less help, in more or less detail. Other
standard parameters allow you to explore where parameters have been set and
where they can be set. The description of the -help parameter is a good
place to start to explore the help available.
The intention of the param package is to provide complete documentation
for the program from the command line.