Same as bitcoin, Dash has a mining network. 
They used to be named as DarkCoin and did a rebranding project that went very well.
The masternodes need to put down a 1000 Dash stake, which prevents any attacker from infiltrating the network successfully.
They'd need to buy a huge amount of Dash to get enough masternodes to launch a successful attack, which makes it practically impossible. So it's defended as well by Proof of Stake.
These masternodes enable:
Instant payment: within 5 seconds! This makes Dash usable for every day spending.
Anonymous sending: privacy is optional with Dash. If you need to for any reason, you can use private send for anonymity.
Governance:
Dash has a treasury. 10% of the mined income and transaction fees goes towards the Dash treasury (currently approximately a $250 000 a month. This is used for marketing, development and everything else. What makes it legitimate is that the community of masternodes get to vote on how the budget is allocated, and can in fact choose to not even pay the original developers anymore if they stop delivering. This holds them accountable while ensuring ongoing development.
About 8% annual interest can be earned on the amount of Dash you put into a masternode. With that you can also vote if you want to, and you can take out your money any time, it is not locked, interest paid frequently.
Good thing with DASH is that they have shown to have a very capable development team that’s addressing a lot of issues as we speak and are also incorporating latest Bitcoin updates into the Dash code.
So that gives me confidence that they are on the right track with making Dash both compatible with Bitcoin and at the same time differentiate itself from Bitcoin by addressing specific weaknesses of Bitcoin.
learn about PIVX a fork from dash here > Cryptocurrency classes