Whitelists and the Address Book
Two lists work together. Each asset's whitelist decides who may hold and move that asset. The workspace Address Book keeps the named addresses you use, so you can whitelist them and send to them without retyping.
#Asset whitelists
Each asset has its own whitelist, enforced by the asset contract for senders and by SQRL Enterprise for recipients. You manage it from the asset's page. See Asset whitelist.
#The Address Book
The Address Book is a workspace list of saved, named addresses: your own vaults, authorised participants, custodians and counterparties. Saving an address does not approve it for any asset; adding it to an asset's whitelist does.
Key takeaway
The Address Book is where you keep addresses. A whitelist is where you approve them for an asset. A destination must be on the asset's whitelist before the asset can be sent to it.