By default, each Aria account is assigned a unique Account Number when created. The Client Account ID is a field that can additionally be set on each account to be tied to your internal CRM application, Production account ID, or other internal systems, for easier tracking and account management.
If a Client Account ID is assigned to an account, this account can be quickly searched for in the Aria Ad Hoc search in lieu of searching by the default-assigned Account Number (Accounts > Search > Ad Hoc).