Hi, I think you may want to use google to get more information on Facebook Open Graph. I would say that Yes, both are necessary for Facebook’s purposes, but I don’t think they are useful for any other purposes (and if someone can enlighten me with contradictory information, that would be great too! I’m only just learning more about Facebook Developer stuff.).
You can also look at the “social” tab on the SEO plugin for some more information and settings around these.
Facebook Open Graph Protocol Information for Developers — that page may be helpful, though I don’t find the writing on the Facebook Developer documentation to be user-friendly (at least for people like me who only want to know a little bit, rather than become OG Masters or something like that).