When you select Scan QR Code from your in-game menu, you can register Pokémon as Seen in your Pokédex.
Players can go to their registered Pokédex Entries, to share QR codes for other players to scan.
These codes were generated so that players can have them Seen in their Pokédex.
Can be useful for finding their habitats in the dex, or having them show up in GTS search function without having to type it's name.
note: if the image says “JP 3DS only”, you’ll need a Japanese 3DS. Additionally, as these entries are not in the Alolan Dex, they’ll be marked as seen (despite not being visible in the Dex) and can be searched on GTS (their name appears under the alphabetical search, meaning users won’t have to type in their names). No other function.