“Shared” accounts are shown in the “What’s ours” view, and are included in your shared net worth.
“Private” accounts are not visible to your partner, and will only show up in the "What's mine" view. If your Private account is being used to fund a Split Goal, it will be displayed as “<your name>’s account” in your partner’s view.
To change your sharing settings, open up the connected account from your Dashboard, or the Accounts page in your Settings. Click on "Account actions" and select "Make private" or "Make shared."