How subnetting works
An IPv4 address is 32 bits, written as four 8-bit octets. A CIDR prefix like /24 says how many leading bits are the network portion; the rest identify hosts. The subnet mask is those network bits set to 1:
The network address is the IP with all host bits set to 0; the broadcast address has all host bits set to 1. The two reserved addresses (network and broadcast) are why usable hosts is 2(32−prefix) − 2.
Worked example
192.168.1.10 / 24:
Reading the result
The host range is every address between the network and broadcast addresses — those are the IPs you can assign to devices. A smaller prefix (say /16) means a larger network with more hosts; a larger prefix (say /30) means a tiny subnet, useful for point-to-point links. A /31 and /32 are special cases with no usable-host subtraction in modern usage.