The Masternodes of the Dash Network are like the Fullnodes of other proof-of-work systems but there are important distinctions.
First of all the Masternodes get compensated with 45% of the block rewards which is important for the scalability of the Dash Network because this provides the owner of the Masternodes with the resources to improve their hardware and internet connection. This is not only important because the blocks and the Blockchain as a whole are growing in size but also because Dashs key features InstantSend and PrivateSend are relying on the Masternodes. They are scheduled to provide even more features in the future which makes technological improvements and financial compensation even more important.
Masternodes have to provide a collateral of 1000 Dash which guarantees them the right to vote in the DGBB. This provides them with a significant influence on the direction Dash is taking and in a figurative sense they can be called shareholders. The collateral is a guarantee that they’ll vote for or against a proposal in line with Dash’s best interest.
A person that wants to own a Masternode needs energy, internet, a dedicated IP-Address, specialized software, reliable hardware and 1000 Dash as a collateral. As soon as the collateral is removed the software and hardware have lost their Masternode status and get counted as a normal Fullnode. Masternodes have to be connected to the internet around-the-clock.
Technological knowledge is a requirement as well. Multiple sources are openly available online and everyone who is interested in the subject can learn it for free.