Every VM connects to a guest network. This page covers the fundamentals - creating additional networks and choosing a network offering.
Guest networks
A guest network is the private network your VM's NIC is attached to. When you deploy your first VM, a default network is usually created for you automatically. As your setup grows, you can add further isolated networks - for example, to separate a public-facing tier from an internal database tier.
Choosing a network offering
Each network is created from a network offering, which determines what services are available on it (DNS, DHCP, firewall, load balancing, VPN, and so on). When creating a new network, pick the offering that matches what you need - a simple isolated network for internal traffic, or one with more services enabled if the network needs to be internet-facing.
Next: VPCs and advanced networking
If you need multiple tiers with routing between them, site-to-site VPN, or a load balancer in front of your VMs, head to VPC & Advanced Networking.