It is a Google shortened URL that translates to the Facebook’s fbsbx.com domain. This is used by Facebook as the domain where the attachments on chats and groups are shared and stored.
They’re not trusted cus their website has danger sign and also they don’t have a good trading platform…
To do so, go to the page, click About on the left side, go to the More Info area, click Add Menu and select the PDF of your menu. You can also share a PDF file with the other people in a Facebook Group. To do that, go to the Group page, click the More button, select Add File and choose the PDF document to upload.
The Facebook Content Distribution Network (FBCDN) delivers photos and videos to people who use Facebook.