What does a masternode do?
-Increasing privacy of transactions
-Doing instant transactions
-Participating in governance and voting
-Enable budgeting and treasury system in cryptos
These masternodes are not standalone but they are always communicating with other such nodes to make a decentralized network and are often referred in short form as MN.
Compare masternodes
https://masternodes.pro/
https://masternodes.online/
Dash Breakdown
45% miners, 45% master node operators 10% DAO
Dash Fork
45% stakes, 45% master nodes (seesaw) 10% DAO
ZCoin fork
70% DAO, 10% smart nodes, 5% miners, 15% stakeholders
PAC-Coin
35% Miners, 45% full nodes, 15% DAO, 5% Charity
It’s possible to buy shares in a dash masternode
http://dashmasternode.org/masternode-shares/