A couples massage books two partners into the same room and the same stretch of time, usually with one therapist each, arranged as a single reservation for two.
Ask ten travellers what a couples massage is and most will picture a spa suite with two tables under one dimmed lamp. The phrase comes from that world, but here it describes something that travels: two people, one room of their own choosing in Amsterdam, and a massage the pair of them share rather than take separately on different evenings.
The word "couples" settles only the number of guests. It says nothing about technique, length or how many therapists come. Those three choices are still yours to make, and they are made together in one message. A pair may want the same technique side by side, or two quite different ones in the same hour. A pair may want a therapist each, or one therapist who looks after both of you in turn. The house reads "couples massage" as two guests first, and then asks which of those shapes you had in mind.
Most couples who use the phrase mean the simultaneous version, with two therapists arriving together. That is also the version the couples massage page describes, priced at EUR 360 an hour because two women are giving their full time at once. The alternative, one therapist and one partner after the other, sits on the ordinary single-therapist rate; the entry on simultaneous vs sequential weighs the two against each other.
Couples on a city break tend to book it on the second or third night, once the museums have been walked and the canal tour done. Others build a whole trip around it: an anniversary, a honeymoon night, a birthday that one partner has kept secret from the other. Friends travelling together sometimes use it too; nothing in the term requires romance, only two adults who are both twenty-one or older and who both want to be in the room.
Every version is outcall. The therapists come to your hotel room, rental apartment or home anywhere central, and nobody walks to a studio because the house does not keep one. What you pay is set by the price ladder, counted by therapists and hours, never by the number of guests.