For an ordinary prefix from /0 through /30, the lowest address names the network and the highest is the directed broadcast address. Addresses between them form the ordinary usable range. That familiar subtraction of two is not a universal rule: RFC 3021 gives /31 a point-to-point interpretation, while /32 identifies one host route.
Ordinary subnets reserve both edges
A /26 contains 2^(32-26) = 64 addresses. Network 192.0.2.128 and broadcast 192.0.2.191 are reserved by the ordinary model, leaving .129 through .190: 62 usable addresses. Host sizing reverses the equation and selects the largest ordinary prefix whose total - 2 meets the requested count.
Name /31 and /32 before counting
On an explicitly selected point-to-point /31, both addresses are endpoint identifiers and there is no directed broadcast; 198.51.100.10 and .11 are both usable. An ordinary LAN request for two hosts still needs /30. A /32 contains one address and represents one host route, so it also has no broadcast. Clear labels prevent the same bit pattern from being explained with the wrong deployment assumption.