"Gibs" are ephemeral
model entities -- that is, transient things like exploded body parts,
or miscelleous office supplies which briefly appear after smashing
apart a breakable file cabinet.
Gibshooter
generates bloody meat gibs
Env_Shooter
generates gibs of your choice
See also Monster_Generic
entity: it allows you to make "monsters" which consist of
nothing more than the model itself (e.g. no artificial intelligence),
including gibs (and furniture!).
And see Monstermaker
-- it makes monsters of your choice (and these will have their usual
artificial intelligence).
Func_Breakable
entities have a Spawn attribute -- this is the entity that will be
spawned when the entity breaks. (You could also use the Trigger attribute
to fire a Multi_Manager when
the entity breaks, which in turn could trigger other entities.)