Boxing is the implicit conversion of a value type to a reference type or to any interface
type implemented by this value type. This is possible due to the principle of type system
unification where everything is an object.
When boxing occurs, the contents of value type are copied from the stack into the
memory allocated on the managed heap. The new reference type created contains a copy
of the value type and can be used by other types that expect an object reference. The
value contained in the value type and the created reference types are not associated in any
way. If you change the original value type, the reference type is not affected. Boxing,
thus, enables everything to appear to be an object, thereby avoiding the overhead required
if everything actually were an object.

Example:
VB.NET
Dim n as Integer = 10
Dim obj as Object
obj = n


Explanation:
In the above code segment, a value-type variable n is declared and is assigned the value
10. The next statement declares an object-type variable obj. The last statement implicitly
performs boxing operation on the variable n.