From Joomla! Documentation
- Save History. (No/Yes). Whether or not to save version history for this component. If No, version history will not be saved for component items or for this component's categories.
- Maximum Versions. The maximum number of versions to store for an item. If an item is saved and the maximum number of versions has been reached, the oldest version will be deleted automatically. If set to 0, then versions will never be deleted automatically. Also, specific versions may be flagged as "Keep Forever" and will not be deleted automatically. Note that versions may be deleted manually using the Delete button in the Version History screen.