What is the main difference between NAT Gateway and Internet Gateway in the AWS cloud platform?

The main difference between NAT Gateway and Internet Gateway in AWS lies in their purpose and traffic direction:

• Internet Gateway (IGW) — a gateway that allows resources within a VPC to have direct internet access and accept incoming connections from the internet. It is typically used for public subnets.

• NAT Gateway — a service that enables resources in private subnets to initiate outbound connections to the internet (e.g., for updates), but does not allow incoming connections from the internet to these resources. NAT Gateway acts as a mediator, hiding private IP addresses.

Example:

• EC2 in a public subnet with an Internet Gateway can directly communicate with the internet.
• EC2 in a private subnet without a public IP uses NAT Gateway to access the internet but is not accessible from outside.

Thus, Internet Gateway provides two-way access, while NAT Gateway provides one-way outbound access for private resources.