Account is the provider account this channel runs under: an ad-account, a page or a mailing-list id. An executor may replace it at launch with the account it actually used.
ExternalID is the provider-side id of the running execution, recorded by the orchestrator at launch and handed back verbatim to read spend or to pause. Server-owned and absent until this channel has launched; anything a caller sends for it is dropped.
Status is this channel's own launch outcome, not the campaign's: pending (added, never launched), live, paused, failed (Detail says why) or unavailable (no executor wired on this deployment). Server-owned — a caller can never assert it.