Bitcoin is a virtual currency that has open source code base and allow us to do peer to peer transaction without relying on centralized third party.
The network is decentralized because any body can support the network, involve in mining and consensus between all the miner is done by the process of "Proof of Work". The miner get the block rewards and transaction fees that act as incentives to the miner to do the mining.
The advantage of having Bitcoin as follows:
You become your own bank and all the funds are in under your direct control.
Bitcoin cannot be counterfeited.