The Token is, in its simplicity, a golden coin with the runes from the Ancients engraved on it.
There are three different ways to earn Tokens. One is by fulfilling the objectives for a level in Sonic Boom: Shattered Crystal. This include clearing a level within a certain time or with a certain amount of Rings. However, there cannot be earned more than one Token from each objective. Other ways include connecting with other players via StreetPass, or playing the daily "Knuckles' Workout" minigame in Knuckles' Hangout. Also, fully assembling the Lost Crystal will earn the player an exclusive purple Token that can be exchanged for an otherwise unobtainable toy.