Account contains your profile and the address the account is registered to. It is reachable from Settings and, separately, at its own page; the two show the same fields.
The address on the account
Password resets, purchase receipts, support replies, export links, notices that a connected social account requires reconnection, and the cancellation link for a scheduled account deletion are all sent to this address. It must remain one you can read.
Accounts are for one person
Sharing credentials shares everything in the account, including the ability to publish to any connected social account. Two-factor authentication is the single most effective control available here and is covered on the security page.
Signing out
Sign out is in this section. In the Mac and iPad applications and in Calamus Ideas for iPhone, signing out removes the stored credential from the system Keychain. Signing out does not revoke device recognition; that is done from Security, and it takes effect immediately from any device.