From wikipedia:
Object-relational mapping (ORM, O/RM,
and O/R mapping) in computer software
is a programming technique for
converting data between incompatible
type systems in relational databases
and object-oriented programming
languages. This creates, in effect, a
"virtual object database" that can be
used from within the programming
language. There are both free and
commercial packages available that
perform object-relational mapping,
although some programmers opt to
create their own ORM tools.
It's good for abstracting the datastore (flat file / SQL / whatever) out in order to provide an interface that can be used in your code. For example, (in rails) instead of constructing SQL to find the first user in a users table, we could do this:
User.first
Which would return us an instance of our user model, with the attributes of the first user in the users table.
