value types are stored on stack whereas reference types are 
stored on heap memory.
dim i as integer
or
int i

i here ia a value type and will be stored on stack.
Actually nearly all the basic types are implemented as a 
structure.
where as
dim i as new Point()
(assuming point as a class)
i here is a referece variable(pointer) and will be stored 
on stack where as The Point object will be created on heap 
and i will point to it.

value types are stored in the memory.
reference types are stored in the heap.
all implicit datatypes,enums,structs are value types.
delegates,objects are reference types..
pointer to the heap where the data is located is maintained 
in the stack
when we delete a reference type pointer to the heap is 
deleted from the stack

Value types directly contain their data while reference 
types store a references to variable's value memory
and value types uses stack to store data amd reference 
types use heap to store data

value refers what is present in the address of the memory
Reference type refers to the address of the memory
Ex:
   int a = 10( here the value stores in the address 'a' and                            the value of that address is 10)
   int b = &a (here the variable b refers the address of 
               the variable a)
here if we print("%d",a) the value prints
here if we print("%d",b) the reference value of a is printed. 
this is the difference between "value" and "reference values"