Every time you edit a page a new revision is created. To view all revisions of a page simply click on the View other revisions link below each page. You can always go back to a previous revision by simply choosing that revision, edit it and save it.
Revisions
Looking at the address bar of your browser you can see the name of this Wiki Page. When viewing a previous revision of this page you'll see the URL looks something like this:
shows the difference from prior author revision where only revisions 3 to 9 are taken into account.
Recent Changes
When editing a page you can use a checkbox labeled "Include page in Recent Changes list.".
If you check this box and save the page then the page will be marked as a "major" revision and will show up in the default listing of Recent Changes.
If you uncheck this box and save the page then the page will be marked as a "minor" revision and not show up in the default listing of Recent Changes.
It is possible to view all recent changes including minor edits, or even to view only minor edits and no major edits. The parameter filter is used to control this aspect:
filter=1 : show only major edits (is the default)
filter=2 : show only minor edits
filter=3 : show major and minor edits
Other parameters to control the recent changes output are: