Two or more pointers have their own Data.
class A
{
string c;
}
A a;
B b;
a=b;//deep copy

class A
{
public A()
{
};
public int i;
}
class TestPerson
{
    static void Main()
    {
A a = new A();
A b;
a.i =5;
b=a; // not a deep copy
b.i = a.i+6;
}
}
here a.i=11 and b.i = 11 because a and b both refer same
instance of object
Deep copy would be implemented in c# using copy construction
class A
{
public A()
{
};
public A(A previouscopy)
{
i = previouscopy.i;
};
public int i;
}
class TestPerson
{
    static void Main()
    {
A a = new A();
a.i =5;
// Create another new object, copying a.
A b = new A(a); // Deep copy using copy constructor
b.i = a.i+6;
}
}
here a.i=5 and b.i = 11 because a and b both refer it's own
instance of object

In C# if u want to deep allocation, u can used 
serialization that is use ISerializable
for shallow copy u can use cloning, that is use Iclonable 
interface

public static T DeepCopy<T>(T obj)
        {
            object result = null;

            using (var ms = new MemoryStream())
            {
                var formatter = new BinaryFormatter();
                formatter.Serialize(ms, obj);
                ms.Position = 0;

                result = (T)formatter.Deserialize(ms);
                ms.Close();
            }

            return (T)result;
        }