Difference between value types and reference types

Value types, as name tells, are values stored in memory; referencer types are (a kind of) pointer to an object (a class, an object, etc...)

From Microsoft:

A data type is a value type if it holds the data within its own memory allocation. A reference type contains a pointer to another memory location that holds the data.

Value Types
Value types include the following:

All numeric data types
Boolean, Char, and Date
All structures, even if their members are reference types
Enumerations, since their underlying type is always SByte, Short, Integer, Long, Byte, UShort, UInteger, or ULong
Reference Types
Reference types include the following:

String
All arrays, even if their elements are value types
Class types, such as Form
Delegates