They're all a little different, but these counters are all coming from the perspective of the hypervisor, looking at resource consumption from the VM world itself. The 5.1 API reference has some better detail:
cpu.usage.*
CPU usage as a percentage during the interval.
- VM - Amount of actively used virtual CPU, as a percentage of total available CPU. This is the host's view of the CPU usage, not the guest operating system view. It is the average CPU utilization over all available virtual CPUs in the virtual machine. For example, if a virtual machine with one virtual CPU is running on a host that has four physical CPUs and the CPU usage is 100%, the virtual machine is using one physical CPU completely.
virtual CPU usage = usagemhz / (# of virtual CPUs x core frequency)
memory.usage.*
Memory usage as percentage of total configured or available memory, expressed as a hundredth of a percent (1 = 0.01%). A value between 0 and 10,000.
- Virtual machine: Percentage of configured virtual machine “physical” memory:
active÷ virtual machine configured size
net.usage.*
Network utilization (combined transmit- and receive-rates) during the interval.
- VM: Sum of data transmitted and received across all virtual NIC instances connected to the virtual machine.