So, VMs are effectively a completely different machine. Different memory space, different disk space, different process space, etc. This is linux applications

So, VMs are effectively a completely different machine. Different memory space, different disk space, different process space, etc. This is linux applications running on the same machine as your windows applications. Yes, they'll be able to talk to each other. Your windows service will be able to talk to a database running from linux and vice versa. The linux processes are still processes running on your windows machine (evidently they're some sort of "lighter process" but that hasn't been explained well... but it was explained that they'll be able to be communicate directly with other processes via sockets, ports, etc). The demos are VERY convincing. Basically everything works exactly like you would want it to work. It's exactly ubuntu and windows running through the same kernel at the same time.