AWS - NAT Gateway vs Internet Gateway

[samaya]

Why we need NAT Gateway and Internet Gateway in AWS?

[Vignesh_T]

Hi Samaya,

An Internet Gateway allows resources within your VPC to access the internet.

NAT Gateway allows resources in a private subnet to access the internet (think yum updates, external database connections, wget calls, OS patch, etc)
It only works one way. The internet at large cannot get through your NAT to your private resources unless you explicitly allow it.

Please refer this discussion too.

AWS - Public Subnet vs Private Subnet

what is the difference between public and private subnet? In which scenario we use the subnets?

Rgds,
Vignesh