From Elendor
@set <object>=[!]<flag name>
Flags give objects certain abilities or qualities. For example,
a wizard player has wiz powers because s/he has the WIZARD flag
set.
Some flags can only be set on certain types of objects, such as
just players or just rooms. Other flags, like VISUAL, can be set
on any kind of object (player, room, exit, thing).
To un-set a flag, use the exclamation point (!) before the flag
name. For help on any particular flag, type help <flag name>.
The list of flags is available in: help flag list
To go into more detail, all objects in the MUSH, like players, rooms,
exits, and things, are essentially the same on the program level. The
MUSH tells things apart by the flags that are set on them. For example,
all rooms have the ROOM flag set on them, just as all players have the
PLAYER flag.
You can see the list of flags set on an object if you are allowed to
examine it. The flags are listed on the line just below the object's
name, after the word "Flags:". Flag abbreviations are also visible
after the object's name in the room description (if the object is not
set OPAQUE).
See also: examine, hasflag(), orflags(), andflags()