Make directory(ies) with the provided name if they do not already exist.
Commonly used options:
-`-p` no error if existing, make parent directories as needed.
-`-v` prints message for each created directory.
Let's say we need to create a directory `dir` in the path `a/b/c/dir`, but directory `b` and `c` don't exist. In this case, `mkdir -p a/b/c/dir` will create the missing directories in the path.