VirtualBox network modes

As covered in the VirtualBox networking docs, the quickest overview into different networking modes is the following table:

VM ↔ VM VM → Host Host → VM VM → Net/LAN Net/LAN → VM
Not attached - - - - -
Internal Network + - - - -
Host-only + + + - -
NAT - + forwarded ports + forwarded ports
NAT Network + + forwarded ports + forwarded ports
Bridged + + + + +

In short, bridged networking happily allows everything, while other less permissive modes give you granular control over your network security.