Gems

Each different gem is unique. There are multiple sets of gems, and there are alot to collect

Why they're in the game
Gems were most likely implemented into the game as a kind of collectible that would keep players hooked trying to find them.

Unfortunatly, they only give you a thing to brag about and are very hard to find, and don't really do anything. But if you dont like scarescraper, it can be a fun pastime.