What's the difference between the Always Display and the Mark as Changed attributes?

You can see the difference between the Always Display and the Mark as Changed attributes when you have a parent child relationship in the extract.

If an attribute is set as Mark as Changed, and a change occurs on the same record, then the application includes this attribute in the output. If no attributes change on the record, but an attribute changes in another record, for example a parent or sibling record, then the application doesn't include the attribute in the output.

If an attribute is set as Always Display and a change occurs on the record or in the hierarchy below the record, then the application includes this attribute in the output. The application includes the attribute even if there are no changes in the attribute's record. If there is a change beneath the record, then it's included.