Bitcoin is virtual currency. it means that in order for a transaction to occur, no middle men or central authority is required.
Better to say bitcoin transaction are p2p based transaction and blockchain is hosted in decentralized environment it doesn't require any central authority and miners verify those transactions.
Being virtual currency doesn't mean it can be transacted without central body, the balance you see in most of the banks right now are also virtual/digital currency but they are centralized one and need central authority to improve every transactions.