How subnetting works
An IP subnet is defined by a network address and a prefix length (CIDR notation, e.g. /24), which together determine how many addresses belong to that network and which addresses are reserved. For IPv4, the network's first address is reserved as the network address and the last is reserved as the broadcast address. Everything in between is usable for hosts. IPv6 doesn't use broadcast, but the same network/prefix math applies to determine a block's address range.
Reading the results
Network Address is the base address of the subnet. Broadcast Address (IPv4 only) is the last address, used to reach every host on the subnet at once. Usable Host Range excludes both reserved addresses. Subnet Mask and Wildcard Mask are two representations of the same prefix length, used by different router/firewall configuration syntaxes.