"A subnet mask is a way to subdivide a classful network into a smaller network that best fits the number of users or devices for your particular network. Subnet masks allow you to create multiple networks and separate networks from each other, thus creating fewer broadcast storms, which can debilitate a network as it grows larger. Subnets also help organize different parts of an organization's devices or users in a more manageable and efficient manner to lessen potential problems with one large private classful network since all devices on that network would receive a broadcast if sent out to the network."