afaik there are no coins. Each account is merely associated with a set of transactions to it. The fees you pay to send money scale with a number of transactions

afaik there are no coins. Each account is merely associated with a set of transactions to it. The fees you pay to send money scale with a number of transactions that got you that money in first place, e.g. if you got $1000 from 1 transaction and send $1000 to someone, you pay less fees than if you got $1000 from 1000 transactions, because making the transaction actually work means joining all these old transactions into a new transaction. Also if you got $1000 from a transaction and need to pay $999 to someone, it will send the whole $1000 you had received to them and create a transaction to send you the change ($1) back.