man package is man page suite, including man, apropos, and whatis consists of programs that are used to read most of the documentation available on a Linux system. The whatis and apropos programs can be used to find documentation related to a particular subject.
man was written by John Eaton. He does not maintain man anymore - please do not bother him with remarks about the current version, which is rather different from the original one.
In man-1.6 Eric S. Raymond's browser-handoff functionality was added, with future minor versions planned to cleanup internationalization and cross platform support (Cygwin, solaris, and perhaps Win32).
There is a very different man program, also derived from John Eaton's original version (by Graeme W. Wilford) distributed under the name man_db, with version numbers like man_db-2.3.10. Do not confuse the two, they are mutually incompatible, although they perform nearly the same job.