A shared email connection is one that had been shared either by yourself or a colleague within Crelate. For further inquiries in regards to setting up and sharing an email connection, please see our Email Configuration article. We also have additional details on Changing your Primary Email Address within Crelate as well.
A shared connection will allow other users, not only yourself, to share from that email address. Typically, this is some sort of email@example.com or firstname.lastname@example.org. This will allow your team to seamlessly send from that address directly within their Crelate account.
When sending an email, by selecting your address in the 'from' line, you'll now have multiple addresses with which to send from.