Exchange currency (denoted as E$ throughout) is the closest thing to the existing currency we use today.  You use it to purchase goods, and when you do, you lose the money.  When you sell goods, you get money.  The only difference in the registry is the amount of currency in costs to the purchaser need not be the same as what the seller gets.

Exchange is owned by you.  You cannot give it to anyone without either exchanging it with charge or value through the registry, even when represented as cash.