The ability to snapshot object data before its state is changed via an update.
The list of objects that support snapshotting can be found using CORE_OBJECT_SEARCH with snapshotavailable='Y'.
You then set which of the objects you want snapshotting to occur on using SETUP_SNAPSHOT_MANAGE.
By default your want see snapshot object data in _SEARCHs to include set custom-option "includesnapshots = Y".
Snapshotting includes structural elements that have extended an objects attributes.