A C++ object with virtual methods and some members looks like this, if you put it in terms of C:

  struct ClassVTable {
   void (*firstMethod)();
   void (*secondMethod)();
  }

  struct Class {
   struct ClassVTable *virt;
   int firstMember;
   int secondMember;
  };

and a pointer to it looks like:

  struct Class *objectRef;

A language that uses fat pointers, like rust, has this separated completely:

  struct Class {
   int firstMember;
   int secondMember;
  };

  struct FatPointerToClass {
   struct ClassVTable *virt;
   struct Class *data;
  }

  FatPointerToClass objectRef; // note lack of pointer, it'd be stored on the stack directly for eg.

This means a much simpler object layout in exchange for passing around larger pointers, and it's a good fit for trait-based typing since it doesn't require you to know all possible interface subtypes of the object in order to describe or use its layout.

(please note that I'm using C struct to be precise about the concept, and this should not be taken as a perfectly verbatim description of the actual object layouts in memory)