From Valve Developer Community
This template isn't in line with anything specific in code. default shows only outputs for brushes.
prop=1shows outputs for props as well. there's nothing brushes have that props don't have.
nohl2=1eliminates the hl2-specific outputs.
- Fired when this object breaks.
!activatoris whatever breaks the object.
- Fired whenever the health of the breakable has increased or decreased. This output automatically puts the new health amount as a decimal percent (e.g. 45% = 0.45) into the parameter box for inputs, if the mapper does not override the parameter with something else.