What ETIAS is
ETIAS is a pre-travel authorisation system for the Schengen Area. It is not the same as a Schengen visa. It is intended for travelers who are visa-exempt for short stays but still need to complete the authorisation step when the official rules apply to their passport and route.
The authorisation is linked to the passport used for the request. If the passport changes, the traveler should check the official ETIAS guidance again before travelling.