The cryptocurrency PIVX, Private Instant Verified Transaction, is a DASH 0.12.0.x fork but in contrast is using a custom Proof of Stake (PoS), instead of a Proof of Work (PoW) system for block consensus. This means that PIVX is not hardware mineable but you can actually earn PIVX as a reward by keeping them in your online wallet. This is called staking.
As PIVX is based on DASH, it has inherited all the technical features of DASH such as masternodes, instant send and private transfer based on the coinjoin method. The PIVX team is currently working to update it to a 0.12.1.x DASH core but with some key differences such as maintaining IPv6 support (as of March 2017).
PIVX has a block time of 60 seconds and has a fixed sized reward per PoS block. However, PIXV uses a custom Seesaw Algorithm that dynamically alters the reward split between masternode and staking nodes. The Seesaw Algorithm is intended to set an incentive for users running masternodes. You can find more information in the PIVX Whitepaper (https://pivx.org/what-is-pivx/white-papers/).
PIVX is also based on a Bitcoin 0.10.x core with some 0.13.2 features committed to the code already. This makes it one of the most up to date proof of stake cryptocurrency on the market.
DASH was a Bitcoin fork, improving the Bitcoin, so a DASH fork, PIVX is improving the DASH.
Another key difference that PIVX is trying to bring to the cryptocurrency space is the implementation of the Zerocoin Protocol with non-optional minting. There are no other PoS cryptocurrencies (as of March 2017) that have a working Zerocoin Protocol implemented. PIVX is trying to be the first to achieve this feat. As we believe every transaction should be private, we will also enforce full-time zerocoin minting transactions by default making every end-to-end transaction untraceable. You can find more information about all features on the PIVX website (https://pivx.org/features/)
We also believe strongly in having an inclusive governance by the community. Thus PIVX is currently (as of March 2017) in the discussion phase on how to further improve the current masternode voting system to allow non-masternode PIVX holders to also be a part of the decision making process and usage of its budget. PIVX has already had numerous publicly viewable live meetings (https://www.youtube.com/watch?v=jF_PWghZaBo) regarding this topic and will continue to do so until a solution is devised and implemented. PIVX main principles are written down in a Manifesto (https://pivx.org/what-is-pivx/manifesto/).