The data on the order (or any object) is being held in a protected member variable
_data which is an array. This data comes from the database table(s) (it is being filled by the resource model).
You can get this array and dump it via:
You will get an output like this with
[entity_id] => 2
[state] => new
[status] => pending
Now you can get all of this data with Magento object's magic getters. Each value is retrievable in the form of
Value is the camel cased version of the key from the array.
For the above values use:
customer_id for example you can call
The getters can be overridden. The getters construction is defined in the
Varien_Object class and each Magento model could override a magic getter method by explicitly defining a method. So you should also check the methods of the model by looking at the code or use hinting in your IDE.