IPv4 addresses are 32-bit numerical labels used to identify devices on a network, written in a "dotted decimal" format (e.g., 192.168.1.1). Each IPv4 address consists of four octets, each ranging from 0 to 255, and is divided into network and host portions. Subnetting is a technique used to partition a large network into smaller, more manageable subnetworks, or "subnets." This allows for efficient IP address allocation, improved network security, and reduced broadcast traffic. By adjusting the subnet mask, network administrators can control the number of available subnets and hosts within each subnet. For example, a subnet mask of 255.255.255.0 (or /24) in CIDR notation allows 256 addresses, with 254 usable for hosts.