The MANPATH environment variable specifies where the man command looks for reference manual (man) pages. The MANPATH is set automatically based on a user's PATH value, but it generally includes /usr/share/man and usr/gnu/share/man.
Note that a user's MANPATH environment variable can be modified independent of the PATH environment variable. A one-to-one equivalent of the associated man page locations with directories in the user's $PATH, is not required.