Value Object
A small simple object, like money or a date range, whose equality isn't based on identity.
With object systems of various kinds, I've found it useful to distinguish between reference objects and Value Objects. Of the two a Value Object is usually the smaller; it's similar to the primitive types present in many languages that aren't purely object-oriented.
for more details go to Chapter 18 of the online ebook at oreilly.com
This pattern is part of Patterns of Enterprise Application Architecture
05 March 2003