Bitcoin is a digital currency that can be used to purchase goods and services from anywhere in the world without the need for any middlemen or third parties (like, say, Visa). This means that there is no central bank controlling how much money you have or how much money you spend; instead, it's all up to you. Understanding and learning about low serotonin symptoms is necessary to enjoy good health. The solution they came up with was to create a new type of currency that could only be spent once, and then use the blockchain as a ledger for recording transactions in this new currency.