SharePoint 2010 includes features that support version control of items in lists and libraries. The SharePoint 2010 publishing features include additional user interfaces to make web content easier for page authors.
Version control allows content authors and approvers to track changes over time. Each list or library has its own settings and you can choose to track only major versions of items, track major versions and minor revisions, or turn of version control entirely.
When you use only major versions or no version control, everyone, including visitors to the site, will always see the current version of each item. A key benefit to using both major and minor versions is that you can configure SharePoint to serve the most recent major version to your visitors while showing the draft version to individuals that can edit or approve the item. This allows authors to make incremental changes to existing pages or create new pages without affecting public views until you are ready for everyone to see the completed, approved, version by publishing a major version.
Traffic Cop and Historian
SharePoint also uses versioning to support collaboration between authors. When you configure versioning on a list or library you will usually also choose to require check-out for editing items. This is the default setting for the pages library in the Publishing Portal.
When you require check-out, you specify that only a single person can modify an item at any one time. This prevents users from creating divergent versions with conflicting changes. As long as an item is checked-out by one user, no other user can edit the item until the user checks it in or until someone with sufficient privileges uses the undo-checkout operation to unlock the item.
It is also possible to allow a user to submit draft items but require approval from another user before a major version is published for consumption by all of a site’s visitors. Approval can be as simple as the click of a button, but it is often augmented by the approval workflow included in MOSS.
If you configure any level of version control, SharePoint will retain the old versions based on parameters you supply. You can limit the number of major versions as well as specify how many major versions for which you want to keep minor versions.
When either limit is reached, SharePoint discards the oldest versions. The publishing features include user interfaces that allow you to see the changes between two versions and it is possible to revert to any previous version at any time as long as SharePoint has not discarded the version.