The Virtualization's network mode

• Host-Only: The VM will be assigned one IP, but it's only accessible by the box VM is running on. No other computers can access it.
• NAT: Just like your home network with a wireless router, the VM will be assigned in a separate subnet, like 192.168.6.1 is your host computer, and VM is 192.168.6.3, then your VM can access outside network like your host, but no outside access to your VM directly, it's protected.
• Bridged: Your VM will be in the same network as your host, if your host IP is 172.16.120.45then your VM will be like 172.16.120.50. It can be accessed by all computers in your host network.

FYI, you can have above 3 modes for networking.  

We NAT because we want VM able to access to network outside world.

We bridge because we want VM to be accessed within host machine's network only.

We host-only because  we want VM tp be accessed by host only.

Hope you like it.