These are the main paid currency in the game and can only be obtained via the store. The price of Genshin Crystals starts from $0.99 for 60 and ends at a price tag of $99.99 for 6480 Genshin Crystals.
Genshin Crystals can also be used to get Primogems and for Wishes. For 10 Wishes, you'll lose 1600 Crystals instantly.