C++ overloading is the mechanism by which the language standard operators are used for customized operations of the classes. For example if we are trying to write a string class, we would very simply ask for "+" operator to handle string concatenation, "-" for removing one part of string from another etc., 
   This will put the users at ease. They need not worry about the internal handling of string operations or memory allocations. Instead they can start writing cleaner code concentrating only on the application functionality. Code Reusability becomes easier. Though the overloaded operators are very cleaner to use, the internals could be a little dirty. That is what, is the only problem/drawback with c++ overloading.   
   The developer of a class with such overloaded operators has to go through a painful set of coding to ensure the users are comfortable ( though at the developer's cost). All the operators can be overloaded except ., ?:, sizeof, ::, .* . Now let us see an example of using the "+" operator. 

//C++ overloading sample 
class MyString 
{ 
  public:
      char member1[100];
      void operator +(MyString val) 
      { 
           strcat(member1, val.member1); 
      }
 };

   The other intricacies of initializing the class, destructors etc., are left out for the sake of simplicity and readability. 
   Similar to the above example of c++ overloading, we can overload all other operators (except some) to give them a meaningful usage for the classes. 
   Usually unary operators may not need a parameter (or may need one at the most) and binary operators may need at least one parameter to be passed inside. This is how most of the times the logic on overloading works( and may differ too sometimes). Also some people will use techniques of passing a parameter to differentiate between a pre fix and post fix operators. 
   The stream operators << and << need a different type of treatment. Though these kind of techniques make the life of the developer difficult, it is the user who is going to be benefited the most.