Host is a representation of an actual hardware or virtual host. It doesn’t matter whether the host is a hardware or virtual (cloud) one, yet the host should be accessible via SSH.
Each host can be added only to a cluster that is already created. The way the host is added into ADCM depends on the type of the selected hostprovider.
You can see the list of hosts at the HOSTS tab.
HOSTS tab in ADCM