mkdir
FilesPackage: coreutils
Creates a directory. mkdir -p also creates missing parents and does not complain if the directory exists — which makes the command rerunnable, but it still fails if a file has that name.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
mkdir -p- Creates missing parent directories, and does not complain if the target already exists.