Network and Host

Every address splits into two parts. The network part says which network the machine lives on, like a street name. The host part says which machine it is on that network, like a house number.

Where the split happens is written after a slash. In 192.168.7.42/24, the first 24 bits (three whole octets: 192.168.7) are the network, and the rest (42) is the host.

Two machines can talk directly only when their network parts match. That single rule is why the split matters so much.