The link in the other reply gives you what you need.
but in essence, OnTap edge is a virtual version on DataOntap that can be deployed in an ESX OVS file, it's fully functional and delivers all of the OnTap features you would expect on a hardware array.
there are some limitations in terms of size etc... it is basically designed for remote office where you potentially don't want a hardware box and maybe you ship a single machine with multiple VM's as part of a remote office strategy.
once the data in on edge it can be mirrored, vaulted etc to central sites for protection purposes.
hope that helps