There are four (4) levels of Scarcity for Sorare cards, for football, all of which you can buy, sell, win, or trade:
⬛ Unique (1 per player per season - this is the only card of its kind in the world)
🟦 Super Rare (10 per player per season)
🟥 Rare (100 per player per season)
🟨 Limited (1000 per player per season)
Common (GRAY) cards have no Scarcity (unlimited supply).
Common cards are given to Managers when they join Sorare to learn more about how to play. They are yours to keep but cannot be sold or traded. They can be used to play in certain competitions.