What Is A subnet
A subnet is a range of IP addresses in your VPC. You can attach AWS resources, such as EC2 instances and RDS DB instances, to subnets. You can create subnets to group instances together according to your security and operational needs.
A subnet is is a network inside a network. Subnets make networks more efficient. Through subnetting, network traffic can travel a shorter distance without passing through unnecessary routers to reach its destination.
In this video we will work you through what is a subnet
Types of subnets
Public and Private subnets.
Public subnet is a subnet that is associated with a route table that has a route to an Internet gateway.
Private Subnet: A private subnet is a subnet that is associated with a route table that doesn't have a route to an internet gateway.
How does a subnet work?
Subnetting divides an IP address into two parts, namely network address and the host address. Then, using the subnet mask technique, you can further divide the divided address into units and assign them to various devices in a network.
How do subnets talk to each Other
All subnets (regardless of whether they are Public or Private) within the same Amazon VPC can communicate with each other by default. Communication should be made through the private IP address of the resources, to ensure that the traffic stays within the VPC.