Layover
A layover is the gap between an arriving and a departing flight; at Schiphol its length decides whether an in-room booking fits and how long it can run.
Airlines and passengers use the word loosely. Some mean any gap between two flights; others keep it for a gap long enough to leave the airport and call anything shorter a connection. For booking purposes the useful definition is practical: a layover is usable when it leaves time to reach a room, spend time there unhurried, and get back through security with margin to spare.
Working out the usable part
Start with the scheduled gap and subtract everything that does not bend. Leaving the aircraft and, for an arrival from outside Schengen, passport control. The walk or ride to the hotel, whether that is a building joined to the terminal or a shuttle out to the business parks at Schiphol-Rijk. Check-in or a day-room handover. Then, at the other end, the return trip, security and, on a departure leaving Schengen, a second passport check. What remains is the window a booking can occupy. On a nine-hour gap that is often three hours or more; on a five-hour gap it may fall under ninety minutes, and sometimes there is nothing sensible left.
Booking it
A layover room is always an airport-area address, so the booking is arranged ahead with a start time fixed in the thread, and half the fee goes before she sets out. Ninety minutes is held by half of its fare, sent in the thread. Message as early as possible, ideally before the first flight leaves, with both flight times and the hotel area, and the office will propose a start that respects the second departure. The layover page covers the sequence on the ground, and transit hotel explains the rooms that make short gaps workable.
If the inbound runs late, the layover shrinks from the front. Tell the booking conversation as soon as the delay is posted, and the reply says whether the booked hour can still hold. If it cannot, a cancellation or a late move is read on the notice scale: nothing kept with more than 24 hours to go, half the deposit inside that window before she leaves, the whole of it once she is on her way, and all of it repaid if someone else takes the hour. The cancellation policy explains where each line sits.