Locate commands by keywork lookup. Apropos displays the man page name, section number, and a short description for each man page whose NAME line contains keyword. It's useful when you have no idea of which man page to look at for certain issues.
e.g. Looking for "player"
At shell, type "apropos player"
Output:
gcd [grip] (1) - A gtk-based cd-player (used as part of grip, or alone) grip (1) - A gtk-based cd-player and cd-ripper gtv (1) - MPEG audio (MP3) and video (MPEG-1) player with GTK+ GUI playmidi (1) - midi file player plaympeg (1) - MPEG audio (MP3) and video (MPEG-1) player splaymidi [playmidi] (1) - midi file player xplaymidi [playmidi] (1) - midi file player gtv (1) - MPEG audio (MP3) and video (MPEG-1) player with GTK+ GUI playmidi (1) - midi file player plaympeg (1) - MPEG audio (MP3) and video (MPEG-1) player splaymidi [playmidi] (1) - midi file player xplaymidi [playmidi] (1) - midi file player xgetfile (1) - X based audio cd player for cdrom drives xlsfonts (1x) - server font list displayer for X xpilot (6) - XPilot/UX Multiplayer gravity war game client xpilots (6) - XPilot/UX Multiplayer gravity war game server xplaycd (1) - X based audio cd player for cdrom drives xprop (1x) - property displayer for X xwud (1x) - image displayer for X