Difference between Internet Gateway and NAT Gateway (Internet Gateway vs NAT Gateway)

There is a minor and confusing difference between Internet Gateway and NAT Gateway. Below are some points to illustrate the difference between both:

1. Internet Gateway is used to connect a VPC to the internet while a NAT Gateway is used to connect the private subnet to the internet (through public subnet and Internet Gateway).

2. NAT Gateway cannot work without Internet Gateway. Your VPC must have Internet Gateway otherwise how NAT Gateway will direct traffic to the internet? NAT Gateway should always be launched in the public subnet where there is a route out Internet Gateway. If there is no route out to the Internet Gateway, NAT Gateway would not be able to connect the instances in the private subnet with internet.

3. NAT Gateway and NAT Instances only support IPv4 addresses while Internet Gateway supports both.

4. NAT Gateway supports only one way communication (from private subnet to internet and not vice-versa) while Internet Gateway supports both inbound and outbound traffic.

I have written a detailed article on NAT Gateway and NAT Instances here. Hope this might help.