Masternodes are a type of full node that keeps the full copy of the blockchain and helps to relay transactions throughout the network. Masternodes also enable features such as instant send and private send.
Instant send is a feature that allows for near-instantaneous transactions, while private send ensures that transactions are kept private. .
Bitcoin does not use masternodes. Instead, it uses a simplified version of masternodes called Bitcoin nodes.
Bitcoin nodes help to relay transactions throughout the network, but they do not keep a full copy of the blockchain nor do they enable features such as instant send or private send.