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 (*sec

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)