A Dash block is simply a block in the Dash open source cryptocurrency blockchain that permits untraceable transactions. The Dash altcoin is a fork of the Bitcoin protocol, but it’s also a decentralised autonomous organisation run by a subset of its users. These users are called masternodes. There are more than 4000 of them and they achieve this position by owning at least 1000 Dash coin. This is how much you have to have in order to be allowed to run a master node. Owning a masternode means that you have voting rights on how the currency itself is run, so you can affect Dash blocks.
But what’s to stop someone buying up all the coins and controlling and laying their claim to all future dash blocks? The current system makes it difficult for anybody to own a majority of masternodes. To do so they would need to buy 2,300,000 Dash coins on the open market, and as soon as it became apparent what they were doing the value of the coins would increase to the point where they wouldn’t be able to afford to buy more.