Revision tracking allows successie changes to a node to be stored, and the differences reviewed. Additionallly, if there are any reasons to do so, these revisions can also be 'rolled back' to a previous baseline.

Revisions are only created if the 'Create new revision' check box is enabled (under the 'Publishing options' group) when submitting the results of a particular node editting session. If that option is not selected, any changes overwrite the previous latest version. The list of existing revisions can be reviewed by selecting the 'Revisions' Tab, which is only accessible when looking at a full node display (as opposed to a teaser).

A 'Diff ' button can be used to compare the differences between two node revisions.  Admininstrators can set up who has rights to do this here.