A Masternode is a server that performs service functions on a blockchain; such as instant send, coin mixing to support privacy, and aids in stabilizing the network. In return, masternodes are paid rewards, dividends in the form of the coin on a periodic basis, for providing important services.
Anyone can run a Masternode and the objective is to have enough online to provide a true level of decentralization, which doesn’t favor a country, a geography, company, or person; assuming the network a network is built to support at a global scale
Masternodes are created when an amount of the coin is sent to the server’s wallet, a form of Proof of Stake – where Masternodes are considered long-term holders, and thus they receive voting rights on the proposals in the network.