Each man section can include a whatis database (/usr/lib/scohelp/LANG/man/.SectionData/whatis/section), which contains the names and description lines of the man pages in the section. These are also merged into a searchable master whatis database, located in the man directory (/usr/lib/scohelp/LANG/man/whatis) and used by man(1), apropos(1bsd), and whatis(1bsd).
The man -k and apropos(1bsd) commands search these records to locate a man page with the given keyword. Here is a sample:
intro (1) - introduction to commands and application programs acctcom (1) - search and print process accounting file(s) admin (1) - create and administer SCCS files alias, unalias (1) - define, display, and remove shell aliases