The following answer is from Gof book (Design Patterns)
An object’s class defines how the
object is implemented. The class
defines object’s internal state and
the implementation of its
operations.
In contrast, an object’s
type only refers to its interface – a
set of requests to which it can
respond.
An object can have many types,
and objects of different classes can
have the same type.
//example in c++
template<typename T>
const T & max(T const &a,T const &b)
{
return a>b?a:b; //> operator of the type is used for comparison
}
max function requires a type with operation > with its own type as one of it interface any class that satisfies the above requirement can be used to generate specific max<particular class/primitive type> function for that class.