Fragments and Memories are the two types of currency used in Arcaea. They are displayed on the upper-right of your screen.
Fragments are mainly used to buy new songs. If you have a surplus, however, you can also spend 1000 to refill your stamina in World Mode. You may only do this once every 2 days. (3 days before v.1.5.2)
You can hold up to 9999 Fragments. Any more Fragments you get after this point will be lost.
Memories are the paid currency in Arcaea. You can buy 100 Memories for $0.99. Individual songs are always 100 Memories to buy, while song packs are generally 500 Memories for the entire set. You can also use 50 Memories to refill your stamina in World Mode.
You must be online and logged in to purchase Memories.