Masternodes are a way to earn high ROI passive income, while still keeping your initial investment.
In order to start running a Masternode, there are a required amount of coins needed. This is different for every Masternode. The amount of coins needed are then staked, earning daily rewards in that corresponding coin. Masternodes get rewarded for verifying transactions in the network.
As with any cryptocurrency, there is a risk involved with Masternodes.