MT::Object is the base class for all Movable Type objects that will be serialized/stored to some location for later retrieval.

Movable Type objects know nothing about how they are stored - they know only of what types of data they consist, the names of those types of data (their columns), etc. The actual storage mechanism is in the Data::ObjectDriver class and its driver subclasses; MT::Object subclasses, on the other hand, are essentially just standard in-memory Perl objects, but with a little extra self-knowledge.

This distinction between storage and in-memory representation allows objects to be serialized to disk in many different ways. Adding a new storage method is as simple as writing an object driver - a non-trivial task, to be sure, but one that will not require touching any other Movable Type code.