What does /24 mean?

It tells you how many bits of the IP address belong to the network portion.

What is a network ID ?

A network ID (or network address) identifies the subnet itself, not a specific device.

It is the first address in a subnet and is used by routers and devices to know which network an IP belongs to.
Example:192.168.1.0

What is a broadcast address ?

A broadcast address is a special IP address used to send data to all devices within a subnet at the same time.

Instead of sending a packet to one device, the network delivers it to everyone in that subnet.
Suppose your subnet is:
192.168.1.0/24
Broadcast address → 192.168.1.255

Why use subnets?

Subnets are used to divide a larger IP network into smaller, manageable networks. They help with organization, performance, security, and efficient use of IP addresses.

Why use subnets?