Many man pages include an index e.g. pkg-info (1) and sometimes the same man page references the same base but with different indices e.g. pkg-info (4).
What does the index stand for?
The index indicates the section the information falls under
will give the man page related to the command and
will give info related to special files for pkg-info
pkginfo(1) -- display software package and/or set information
pkginfo(4) -- package characteristics file pkginfo is an ASCII file that describes the characteristics of the package along with information that helps control the flow of installation.