Just to add some accessibility information to the above, you can see the manifestation of the man pages directory structure by adding a section number to your command when calling up a man page.
For example, running
man printf on Linux brings up the User Commands man page for the
printf utility in section 1 of the man pages. On BSD
man printf brings up the analogous BSD General Commands Manual man page for
printf in section 1.
Alternatively if you run
man 3 printf on Linux you'll get the Linux Programmer's Manual man page for the
printf family of functions in the C programming language in section 3 of the man pages. On BSD
man 3 printf brings up the analogous BSD Library Functions Manual man page for the C
printf functions in section 3.
When just running
man foo the man utility will begin its search in section 1, and proceeds through to higher numbered sections until it either finds the man page for
foo, or exhausts the search. You can see what section a man page is in by looking at the first line of the man page. In the upper right or left you'll see
N is the section number, corresponding to the directory structure of the man pages.
In contrast to running
man foo and searching through all sections until the first hit, running
man N bar where
N is the targeted section, will restrict the search to just that section.