Boxing means convert value type to reference type

converting value type to reference type is called boxing.

Boxing is nothing but converting value type to reference type
Example:int i =10;
        object o = i; \\Boxing which can happen implicitly
     
       int j = (int)o; \\Unboxing Converting Referrenvce Type 
                         to value type.

Boxing is the process of converting a  value type to the
type object or to any interface type implemented by this
value type. When the CLR boxes a value type, it wraps the
value inside a System.Object and stores it on the managed
heap. Unboxing extracts the value type from the object. In
the following example, the integer variable i is boxed and
assigned to object o.
Exam::
int i = 123;
object o = (object)i;  // boxing
...........
o = 123;
i = (int)o;  // unboxing