Horizen is an open, interoperable blockchain ecosystem that is supported by decentralized muli-tiered node infrastructure. It focuses on scalable data privacy, using unique sidechain technology called Zendoo. Horizen is a fork of Zcash, therefore uses the same technology which is Zk-SNARKs, to provide privacy, security and interoperability.
ZEN is the native cryptocurrency for Horizen ecosystem. It is used to fuel the ecosystem by giving rewards miners and secure nodes, and can also be traded in the open market.