"Let’s get this out of the way. Object databases aren’t just for ninjas although they are often wielded by ninjas. An object database is exactly what it sounds like, a database for your objects. No sql, no tables, no object-relational impedance. Just objects persisted similar to how a relational database allows you to store and persist tabular information offline without all the grief of mapping your object-oriented structure onto a relational model. Instead you create your objects and using the database’s API you can save and query for your data without worrying about sql or any of that mess. My personal favorite OODBMS (object-oriented database management system) is db4o. I recommend downloading and playing around with it to get a feel for how simple it is to use."

MICHAEL D. HALL in "The Poor Developer’s Object DataStore"