Getting ready

A UObject is the base class of all UE4 class objects, while an FStruct is just any plain old C++ style struct. All objects that use the automatic memory management features within the engine must derive from this class.

If you may recall from the C++ language, the only difference between a C++ class and a C++ struct is that C++ classes have default  private  members, while structs default to  public  members. 

In languages such as C#, this isn't the case. In C#, a struct is value-typed, while a class is reference-typed.