Internet gateways

An internet gateway, commonly referred to as an IGW, is used to help create a public subnet. It is a logical component that you must create and attach to your VPC to allow traffic to traverse from your subnet in your VPC out to the internet and vice versa. Without an IGW, there is no link or connection between your VPC and the outside world. 

Later in this chapter, I will show you how to build a multi-subnet VPC with an IGW. This will look at how to create and attach it to your VPC.