vbox networking

NAT - Your host will act as a router (firewall) and your guests will be on a private subnet. Use this if you are not running servers on the guests.

Bridged - Your guests will get a ip address on the same subnet as your host.

Internal networking

    This can be used to create a different kind of software-based network which is visible to selected virtual machines, but not to applications running on the host or to the outside world.
Host-only networking

    This can be used to create a network containing the host and a set of virtual machines, without the need for the host's physical network interface. Instead, a virtual network interface (similar to a loopback interface) is created on the host, providing connectivity among virtual machines and the host.