Boxing :
Boxing is the process of converting a value type to the object type.When the CLR boxes a value type, it wraps the value inside a System.Object and stores it on the managed heap.
Example :

int i = 123;    
// The following line indicates the boxing of i.
object o = i;

Unboxing :
Unboxing is an explicit conversion from the type object to a value type

 o = 123;
// The following line indicates the unboxing of o.
 i = (int)o;