Zend certified PHP/Magento developer

Why VMWARE is asking me to select the OS when there is an OS in the Iso?

I am using Vmware and I downloaded a Kali Linux Iso. This means that a linux OS is inside the ISO, right? If that’s the case why do I need to choose a OS when creating a Virtual Machine in Vmware?

I want to understand what is happening. Does Vmware provide the OS and the ISO only the file system? How does that work?

Vmware asking me to choose an OS