Ballooning is a technique for VMware ESXi hypervisors to reclaim memory from virtual machines that they host. For VMware environments, Turbonomic discovers utilization of ballooning and considers ballooning in its analysis.
On the host, a balloon driver runs in the VM guest OS. When the host needs more memory, it can “inflate” the balloon on the VM to claim physical pages on the guest OS. The VM cannot use that memory, which leaves it available for the host to allocate to other consumers. The host drives ballooning when it is low on memory. If the host is in a healthy state, you should not see ballooning on the hosted VMs.