The only part of Moodle with this facilty (as far as I am aware) is the Wiki module that stores a complete history of edits in the standard Wiki manner. For other items very basic tracking is provided by the logs and I believe text resources have a last modified date at the bottom.
More robust version tracking is something that we (Howard Miller and I at Glasgow) have been considering adding to the text resources though it's purely at the conceptual stage at the moment.