It is the technique whereby you tie the properties of data defined in Object-Oriented terms with data defined in Entity-Relational.
The problem it is designed to solve is called the "Object-Relational Impedance Mismatch". Have a google, if you want to know more.
As for a real world example: any time an OO applciation uses a Relational database is a candidate for ORM. [ June 05, 2007: Message edited by: Paul Sturrock ]