The Hierarchy in Unity is a complete list of any object in your open scene.
Objects are listed from A to Z order,
but it is also possible to create hierarchies of objects
which are in turn listed in A to Z order.
Hierarchies of objects mean that they are grouped, with the top most object being called the Parent Object
and the rest being referred to as Children or Child objects.
These objects then have their transform values based upon that of their parent object.
For example the position of an object when loose in the hierarchy
is based on it's distance from the world origin, or zero point.
But when this object is made a child of another object it's position is relative to that of it's parent.
In this example the character object is at the origin of the 3D scene,
the position (0, 0, 0).
And there is a cube object at position (5, 1, 5).
But when the character object is made a child of the cube - it's origin, or zero point,
is then the position of the parent object, the cube.
Now the character's position is said to be (-5, -1, -5).
This being the distance from the cube object, it's parent and therefore it's origin position.
We can also see that with Pivot Point Rotation enabled
the rotation is now based on the parent object
rather than rotating around it's own axis.
The same then applies to movement,
and scaling.
And this will apply until that object is no longer a child.
Other features of the hierarchy are the Create button
and Search field.
The create button on the hierarchy acts as a mirror of the Game Object - Create Other top menu
and this will allow you to create various different things that you will need to construct your games in Unity.
Whilst the search field works in a similar way to the search field in the Scene view,
allowing you to narrow down objects using their name.
The scene view then reacts by greying out other objects
allowing you to see the object you've searched for more easily.
You can also make use of the modifier T: in order to search for types of object.
Type here being considered as one of the objects components.
For example if I search for T:Light
there is only one light in my current scene,
one on the end of the players gun.
And if I search for T: Audio Source
I'll be narrowed down to 3 objects,
the only ones in the scene that happen to have audio source components attached to them.
When searching in this way, the bottom of the hierarchy shows the path to the object that you've found.
Damage audio source being the one I have selected,
Player being it's parent and Cube being the parent of that object.
This means that when cancelling the search you can easily see where your object is.
It will also remain selected and the parent objects of that object will be expanded to show where it's located.
Subtitles by the Amara.org community