When a group of entities are parented together, they form a rigid movement hierarchy family which will move together as if all the entities were one physical object. Each child-entity will follow its parent's movement. (All entities can have parents, but may not necessarily function correctly).
This can be very useful to make for example: A door with breakable glass, you only need to parent the func_breakable to the func_door and VOILA!
Items Required (itemsrequired)
Add one or multiple item_generic data names (max 4) that you need to have in your inventory in order for this entity to work. Separate each data name with a space.
Objectives Required (objectivesrequired)
Add all the objectives that need to be completed in order for this entity to work. Separate each objective with a space.