1 – if you need to refresh an olde version of CMS for a client. That website is full of trash (old modules/plugins/code) and you wish to keep only the page contents

2. If you just want to replace the page content keeping all modules. Very useful when you create a new website from an old one.

Tables you have to replace (or just their content)
_content
_content_seq
_content_props
_content_props_seq
_crossref
_css
_css_seq
_css_assac
_htmlblabs
_htmlblabs_seq
_templates
_templates_seq
_ userplugins
_userplugins
_userplugins_seq

To replace just go into admin (phpmyadmin) empty existing table and insert new content (taken from export for example)