What does a larger prefix length signify for a subnet mask?

A larger prefix length in a subnet mask indicates that more bits are being used to identify the network portion of an IP address, which directly impacts the number of subnets and the number of available hosts within those subnets. With more bits allocated to the network portion, there are more possible network addresses (subnets), but fewer bits are left for the host portion.

This means that while you can create more subnets due to the increased prefix length, each subnet will have a smaller number of IP addresses available for hosts. For example, if the prefix length increases from /24 (which allows for 256 addresses, with 254 usable for hosts after network and broadcast addresses are deducted) to /28 (which allows for 16 addresses, with 14 usable for hosts), the number of available subnets significantly increases while the number of hosts per subnet decreases. Consequently, a larger prefix length corresponds to a scenario where there are more subnets created but fewer available addresses for hosts within each subnet.