Each infrastructure is a unique VPC, in a region with a Kubernetes (or ECS cluster or both). Infrastructure can be created with 4 basic inputs: Name, VPC CIDR, Number of AZs, Region and option to enable or disable a K8S/ECS cluster. Behind the scenes, the system will automatically create the subnets, NAT gateway, routes and the cluster in the given region.
Infrastructure Creation Screen
If the Infrastructure requirement is to configure in custom Private/Public Subnet CIDR, it can be achieved using Advanced Options.
A common use for Infrastructure is having for instance 2 infrastructures, one for prod and one for non-prod. Another one is having an infrastructure in a different region either for DR or localized deployments for clients in that region.