May I add, regarding Schiphol (AMS):
The terminal building is divided into three 'halls'.

Hall 1 is for flights to countries within the Schengen area.
This encompasses flights from Pier B and Pier C.
It has most of the usual facilities, including a KL lounge. No hotel, or library, or art gallery, mind.
There is normally no immigration control within Hall 1. However, in the event of random checks, one should be carrying an ID, and a passport is normally the acceptable ID. Residents of the Schengen area tend to be allowed a national ID card, where this exists.

Halls 2 and 3 are for flights to outside the Schengen area.
They encompass Piers D E F G and H.

However, Pier D is sometimes also used for flights to the Schengen area. For this purpose, it has been (re-)built on two levels, which allows it to function in 'dual' mode, for both Schengen and non-Schengen flights.
Someone more knowledgeable on Pier D's split functionality is welcome to add here!

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For historians and nostalgians, the original stump of Pier D, the first 150m, before it bifurcates left and right, is the (site of) the original sole pier of Schiphol.
One arrived, went downstairs to immigration and baggage, and the sole arrival hall. Underneath this and the car park outside was a set of spaces for railway lines and platforms. The railway came later, but was planned for at the outset - those planners must have had their visions in the mid-50s.!
Not long now, and it will be time to celebrate the 100th century of the original plans for this new Schiphol, to replace the initial sheds over in what is now Schiphol-Oost. What a novel idea! I hope SPL management will invite me to the party!

And on the departure level upstairs, one passed passports, down three or four steps, and strode straight ahead down the pier to one's gate. That differential in height is still there.
FlyerTalk came later.