Let's dissect the default templates and how they operate. We only linked a single template, and it ended up discovering all hypervisors and virtual machines; it's time to find out how that happened. The top-level template, Template VM VMware, also does some direct monitoring, although not much; it has items for VMware Event log, Full name, and Version, as shown in the following screenshot:

These would be collected on the vCenter or vSphere level. It all grows more interesting and complicated when we look at the LLD rules on this template. It discovers VMware clusters, hypervisors, and individual virtual machines. Admittedly, cluster discovery isn't that complicated; it only has a single item prototype to monitor cluster status. Hypervisor discovery uses an LLD feature we haven't looked at yet: host prototypes.