You have heard about VPCs and subnets. What are the differences between these two?
A subnet is a subdivision of a network. Internal to an enterprise network, you may divide the network into different addresses with gateways, routers, bridges and subnet masks. The subnet mask (in CIDR (classless inter-domain routing) notation may be /28, /24, /10 etc.
A VPC ordinarily has its own NACLs and firewalls associated with it; these are usually part of the public cloud's built-in features. For AWS the firewall is called a Security Group. In AWS you can configure a VPC's availability zone, give the VPC a name, add service endpoints, add route tables, configure peering connections (with other VPCs) and select a hardware tenancy type (either shared or dedicated). In AWS a VPC will have a public subnet. VPCs also exist in IBM's public cloud, Azure, and GCP.