Sometimes merchants creates many cms pages with important contents for customers. Sometimes these pages contains valuable informations related to products, categories, refunds etc. A lot of users share these pages on facebook timeline. Facebook to display stuff on timelines searchs on shared pages for open graph tags. If cms page is without open graph tags facebook will display random contents - these contents usually aren't related to cms page (weird picture, wierd description, weird title etc.)
Sadly, prestashop hasn't got feature to define open graph tags for CMS pages (and to define open graph tags at all). In this case we have to do some workarounds, especially when we want to use different open graph tags for each cms page that we have. We can add custom open graph tags like OG:IMAGE, OG:TITLE, OG:DESCRIPTION with html box pro module. This addon allows to place custom contents on selected pages, we can of course select where the contents will appear (in this case: header hook).
watch how easily you can define open graph tags (example based on OG:IMAGE) for cms pages!