They have been around for a long time and were one of the first to have a hyper-converged solution where all storage in the nodes is pooled and usable by any node. They also have their own hypervisor. You can get 4 nodes per 2U so pretty dense. In the datacenter my company uses a company had dozens of Nutanix boxes sitting in the hallway for months before they finally installed them. They are pretty notoriously expensive so only really used by companies with big IT budgets.