Each time you save a piece of content, you create a revision of it and all its components in Drupal. You can access, review, and revert these revisions by navigating to the content, clicking Edit Page in the admin bar at the top of the screen, and selecting Revisions.

A screenshot of the administration interface for viewing revisions of a piece of content.

Each revision is shown in reverse chronological order with a timestamp of when it was created and the Workflow state it represents, either Draft, Published, or Archived. On the right side of this list are radio buttons which allow you to select two revisions and a button below to compare the revisions. You can also choose to Revert to a particular revision, which will make that the current state of the content.

Comparing Revisions

By selecting two revisions and clicking the Compare selected revisions button you can view the differences between those changes. Content which was removed will appear in red and content which was added will appear in green. There are several view modes available. See below for some examples.

The Drupal revisions interface for a piece of content using the Visually Inline view mode. The text "Path" has been removed and replaced with several lines of text about URL paths.
The Visually Inline view mode for revision comparison.
The Drupal revisions interface for a piece of content using the Unfied Fields view mode. The text "Path" has been removed and replaced with several lines of text about URL paths.
The Unified Fields view mode for revision comparison.