Differences between Kali ISOs?

Hi, I would know what are the differences between the vm-designed Kali Linux ISO and the "normal" one. Yes the vm-designed one is as "vm ready file", already configure and all the stuff... but what are the real differences, for example it says on the website that the vm one is isolated, but is this already not the case of a vm? And what is snapshots and vagrant image? thank you