Juan Carlos S. answered 04/10/19
3D Instructor for Maya, 3DS Max, Zbrush, Blender, Fusion 360, and more
Hi,
A smart object is a layer which content is "protected" sort of saying to work non-destructive. You can apply a free transformation and later on you can come back and remove it. For example, you can rotate and scale the smart object and later on come back to remove those transformation and leave it on the initial state. It is also very helpful when applying filters. On a regular layer when you apply a filter you can't modify it, unless of course that you undo and do it again. When you apply a filter to a smart object you can always come back and change, as many times as you wish, the options on the filter to change the result. For Example, if you apply a blur to a regular layer and later on decide that you need to change to more/less blurred you will have to bring back the original layer and apply the filter again. If you apply the filter to to a smart object you can come back at any time, double click the effect on the layer and change it. Also, smart objects are used all the time when doing muck ups, so you can alter the content of the smart object keeping all the modifications and effects you have applied to it. I hope this help.
JCS
PS: If it is not clear, we can connect sometime and I can give you a short class for free to show you the best ways to use the smart objects.