VMware virtualizes away the underlying hardware. So, if you give the VM a single CPU, then it will run on only one core in the chip. The VM Does not see the entire chip, so it cannot see all cores. If your VM needs to use multiple cores, then it will need to be set for Virtual SMP if you have it.

The reason it is done like this is so that if you had, say, 4 VMs on the machine, each would have its own core. It is more efficent that way.

So, to answer your question, VMware treats a core as an individual CPU when virtualized.