CIDR Guide
CIDR notation is an address, a slash, and a prefix length. The prefix length is how many leading bits stay fixed for every address in the block. The subnetting guide walks the same idea from first principles.
A prefix of 24 means the mask is twenty-four 1 bits: 255.255.255.0. The remaining 8 bits are host bits, so the block holds 256 addresses.
A /24, read from 192.168.1.50
The host bits are cleared to find the network, then set to find the broadcast.
Network 192.168.1.0. Broadcast 192.168.1.255. Usable hosts 192.168.1.1 through 192.168.1.254, which is 254 addresses. The wildcard is 0.0.0.255.
Open this block in the subnet calculator or scan every prefix in the CIDR reference.
192.168.1.50/24 mask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 usable 192.168.1.1 - 192.168.1.254
What the slash does not mean
The number after the slash is not a count of hosts. /24 is not 24 hosts. It is 24 network bits, and 8 host bits.
/31 and /32 are still prefixes. A /31 has two addresses, both usable on a point-to-point link. A /32 is one address. The full table, including those two rows, is the CIDR reference.
Questions
No. 192.168.1.50/24 names the same block as 192.168.1.0/24. The prefix, not the host bits you typed, decides the network.
A contiguous mask converts to exactly one prefix. 255.255.255.0 is /24. A mask with the 1 bits broken up, such as 255.255.0.255, is not a prefix.
