UObjects and Actors
Actors are instances of classes that derive from the
AActor class; the base class of all gameplay objects that can be placed into the world. Objects are instances of classes that inherit from the
UObject class; the base class of all objects in Unreal Engine, including Actors. So, in reality, all
instances in Unreal Engine are Objects; however, the term Actors is commonly used to refer to instances of classes that derive from
AActor in their hierarchy, while the term Objects
is used to refer to instances of classes that do not inherit from the
AActor class. The majority of the classes you create will inherit from
AActor at some point in their hierarchy.
In general, Actors can be thought of as whole items or entities, while Objects are more specialized parts. Actors often make use of Components, which are specialized Objects,
to define certain aspects of their functionality or hold values for a collection of properties. Take a car as an example. The car as a whole is an Actor, whereas the parts of the car,
like the wheels and doors, would all be Components of that Actor.