XP does this while the initial PlanningGame is in process. It's not an iteration - it might be longer or shorter, we don't know yet. What it's about is exploring solution elements that seem relevant to the as yet limited knowledge we have about the problem domain, choosing a SystemMetaphor, putting enough of our build, dbms, and source control tools in place to be able to begin controlled work, and then proceeding ModelFirst until we have something that runs and can be iterated.
Does this have another name?ExplorationPhase of ReleasePlanning
XP "prefers" this practice to a Prototype, because the latter often intends to impress a gullible OnsiteCustomer with a stage-prop demo. Those are easy.
An ArchitecturalSpike intends to identify areas of maximum risk, to get started with estimating them correctly.