Method/function arguments are invoked according to call-by-value. This means that values are copied with invocations to constructors and destructors as a result. This does no harm for basic data types, simple objects and pointers, but reduces performance for complex objects. When arguments are passed using references (call-by-reference), only the reference itself is copied.

void SetComplexObject(const ComplexObject sName);    // Less efficient.
void SetComplexObject(const ComplexObject& rsName);  // More efficient.

struct Coordinate {
  int x;
  int y;
  int z;
};

and

class Product {
  ...
private:
  Coordinate loc;
  float price;
};

are considered simple objects in this context.