Om Next is the successor of the clojurescript library om.
From https://github.com/omcljs/om/wiki/Quick-Start-%28om.next%29 :
Om Next is a uniform yet extensible approach to building networked interactive applications. By providing a structured discipline over the management of application state, Om Next narrows the scope of incidental complexity often found in user interface development. The Om Next discipline is founded upon immutable data structures, declarative data specifications, and a simple convention for routing data access and mutations.
Om Next borrows ideas liberally from Facebook's Relay, Netflix's Falcor, and Cognitect's Datomic. If you are not familiar with these technologies, fear not, this tutorial makes few assumptions. You will be guided through all the core concepts of Om Next. This will prepare you for later tutorials that show custom storage integration and transparent synchronization between your UI and a remote service.