Rarity

Rarity is the range of difficulty on how hard it is to get a specific card. The spectrum is on five different points: Common, Uncommon, Rare, Very Rare, and Super-rare.

Symbols

 * 64: The symbol 64 stands for Common, the easiest to find of them all. It represented the 64 in Nintendo 64 game console. The maker was thinking of using NES instead.
 * 128: The Symbol 128 stands for uncommon, slightly harder to find than common. It represented the supposed sequel to Super Mario 64. the maker thought of using SNES instead.
 * N: The Symbol N stands for rare, harder to get than 128 but still easy. N stands for the Nintendo in the Nintendo 64 game console.
 * GC: The symbol GC stands for very rare, a very hard to get card. GC stands for Gamecube, one of Nintendos consoles and the one with many best-sellers.
 * Wii: The Symbol Wii stands for Super-rare, the hardest to get type of card. Wii stands for the current Nintendo console.

Reason
The reason rarity was introduced was to make sure that it wasn't that high of a chance to get one of the better cards more often than the bad ones. Although, some cards are easy to get but very strong.