From Bulbapedia, the community-driven Pokémon encyclopedia.
The promotional disks are a special collection of disks used with the Pokémon Ga-Olé arcade game that cannot be obtained under normal conditions. Special disks (スペシャルディスク) include those available as giveaways, included with items of merchandise, or by playing courses unlocked by scanning Ga-Olé Tickets. Special disks can come in a variety of colors. Trophy disks (トロフィーディスク) are purple and are usually awarded as participation prizes in Pokémon Ga-Olé events. All promotional disks have the collection number "P".