Wiki: worldspawn

worldspawn - Brush Entity

A special entity that controls several global properties. Created automatically, and can be found in Hammer under Map > Map Properties.

Map Description/Title (message) - Used to show the map's title/description in the old WON interface.
Environment Map (skyname) - Lets you choose what sky image you want. See: Sky List
CD track to play (sounds) - 0 or 1 = None. CD track to play when the level begins. See also: trigger_cdaudio and target_cdaudio
Default light level (light)
Default Wave Height (WaveHeight) - Set the default wave height here (can be overridden by the properties in func_water).
Max viewable distance (MaxRange) - Maximum distance the player can see in Hammer grid units; same as sv_zmax.
Chapter title message (chaptertitle) - Text displayed when entering the level. See also: game_text and env_message
Level Fade-in (startdark) - 0 = No, 1 = Yes. If Yes, then the level will start black and fade into normal light. See also: env_fade (Not available in Deathmatch Classic)
Display game title (gametitle) - 0 = No, 1 = Yes. If Yes, then "Half-Life" will be displayed after the map loads.
New Level Unit (newunit) - 0 = No, 1 = Yes. If Yes, all previous global triggers will be removed. See also: env_global.
Map team List (mapteams) - This will be copied into the mp_teamlist while your map is running if the server allows maps to override the team list.
Default Team (defaultteam) - 0 = Fewest Players, 1 = First Team (team index 0). See also: game_player_team, game_team_set and game_team_master

Every common brush (that is not a brush-entity) is part of the whole "worldspawn".
chaptertitle is only shown in single-player maps.