A brand New concept in the Seventh Generation is that of QR Scanning, a feature that can be accessed on the lower screen menu while playing your game. This feature allows you to Scan QR Codes of given Pokemon, which will in turn be registered to your Pokedex as being Seen. From there, a player can locate the Pokemon in their given games, that is if it can be found in such. However, a player can only scan ten given QR Codes at any one Time before the Scanner must take time to regenerate.
After catching a Pokemon Species, a player can view that Pokemon's QR Code by going into their Pokedex and viewing that Pokemon's information. Players can then share these codes with friends and others, allowing them to scan the Pokemon QR Code into their Pokedex by using their won 3DS and then being able to search for it on their own. However, Legendary Pokemon, Mythical Pokemon, and other certain Pokemon like Type: Null will not have a QR Code show in their Pokedex Entry.
See all the available codes here
After scanning each QR Code with your QR Scanner, you will receive 10 points for your QR Scanner. After scanning ten different QR Codes and earning 100 Points, a player can perform what is called an Island Scan. With this Scan, the Scanner will scan the current Island in Alola you are on and tell you were you can find a rare Pokemon with a special move on that island. There is one specific Pokemon for every item per day of the week, meaning a total of 28 "Rare" Pokemon can be found by using the Island Scan.
Island Scan Pokemon
Totodile - Melemele Island - Mondays
Deino - Melemele Island - Tuesdays
Horsea - Melemele Island - Wednesdays
Klink - Melemele Island - Thursdays
Chikorita - Melemele Island - Fridays
Litwick - Melemele Island - Saturdays
Cyndaquil - Melemele Island - Sundays
Spheal - Akala Island - Mondays
Luxio - Akala Island - Tuesdays
Honedge - Akala Island - Wednesdays
Venipede - Akala Island - Thursdays
Bellsprout - Akala Island - Fridays
Marill - Akala Island - Saturdays
Gothita - Akala Island - Sundays
Swinub - Ula'ula Island - Mondays
Duosion - Ula'ula Island - Tuesdays
Roselia - Ula'ula Island - Wednesdays
Staravia - Ula'ula Island - Thursdays
Vigoroth - Ula'ula Island - Fridays
Axew - Ula'ula Island - Saturdays
Rhyhorn - Ula'ula Island - Sundays
Conkeldurr - Poni Island - Mondays
Togekiss - Poni Island - Tuesdays
Leavanny - Poni Island - Wednesdays
Serperior - Poni Island - Thursdays
Samurott - Poni Island - Fridays
Emboar - Poni Island - Saturdays
Eelektross - Poni Island - Sundays