Masternode is simply a cryptocurrency full node or computer wallet that keeps the full copy of the blockchain in real-time. But masternodes are considerably different in their functionality than normal nodes. They are different because they perform several other functions apart from just keeping the full blockchain and relaying blocks/transactions as a full node does.

- Increasing privacy of transactions
- Doing instant transactions
- Participating in governance and voting

Masternodes are very useful for crypto investors because of running a masternode you are incentivized. Consider it just like earning a monthly or weekly interest on your crypto holdings. Basically you are rewarded for helping to maintain the integrity of the blockchain network.