What is VPC, Subnet in AWS
What are AWS VPCs (virtual private clouds)? What practical purposes do they serve? Is it mandatory to launch instances within a VPC?
What are the subnets and why are they necessary? Do subnets correspond to a particular region?
Answer
At a high level, you can think of a VPC in AWS as a logical container that separates resources you create from other customers within the Amazon Cloud. It is you defining a network of your own within Amazon. You can think of a VPC like an apartment where your furniture and items are analogous to databases and instances. The walls of your apartment isolate and protect your things from being accessible to other tenants of the apartment complex.
Subnets would then be analogous to the different rooms in your apartment. They are containers within your VPC that segment off a slice of the CIDR block you define in your VPC. Subnets allow you to give different access rules and place resources in different containers where those rules should apply. You wouldn't have a big open window in your bathroom on the shower wall so people can see you naked, much like you wouldn't put a database with secretive information in a public subnet allowing any and all network traffic. You might put that database in a private subnet (i.e. a locked closet).