Object-Relational mapping (O/RM, ORM, and O/R mapping) is a
programming technique that links databases to object-oriented language
concepts, creating (in effect) a "virtual object database." The
package that implements the Object relational Mapping is known as Object
Relational Mapper or ORM. ORM can be used in an n-tier application. There are
many ORM packages available in the market both for free and commercial usage. However,
some programmers develop their own ORM packages for the same.