Variable Length Subnet Masking (VLSM) is a technique used in computer networking to allocate IP addresses more efficiently. Unlike traditional subnetting, which uses a fixed subnet mask for all subnets, VLSM allows different subnets to have different subnet masks based on their specific needs. This flexibility helps optimize the use of available IP addresses. By applying VLSM, network administrators can create subnets of varying sizes, accommodating different numbers of devices. This approach reduces waste and improves overall network performance, making it particularly useful in large networks where address space is limited.