IP addresses enable resources in your VPC to communicate with each other, and with resources over the Internet.
EC2 and VPC support IPv4 and IPv6.
By default, EC2 and VPC use the IPv4.
When you create a VPC, you must assign it an IPv4 CIDR block (a range of private IPv4 addresses).
Private IPv4 addresses are not reachable over the Internet.
To connect to your instance over the Internet, you can assign a globally-unique public IPv4 address to your instance.
All subnets have a modifiable attribute that determines whether a network interface created in that subnet is assigned a public IPv4 address and, if applicable, an IPv6 address.