You need to get a 20 port Ethernet Switch.
(or "link" two 10-port or "link" four 5-port). Then connect each computer to the switch. They can all talk to each other.
The arrangement of computers in a network is known as Network topology.
A group of computers might form a network, but this is not necessarily the case. There is no commonly used collective noun for computers.
Servers
Two or more computers connected together create a computer network. Computers within a network can interchange data.
Not all - although most 'modern' computers do. Modern computers tend to be supplied with either an 'on-board' network adaptor or network card plugged into one of the slots on the motherboard. Older computers came without a network card, and needed additional hardware to connect to a network.
It is the relation between computers in network.
That is a printer that is accessible to computers in a network
That is a printer that is accessible to computers in a network
proxy or firewall
Not all - although most 'modern' computers do. Modern computers tend to be supplied with either an 'on-board' network adaptor or network card plugged into one of the slots on the motherboard. Older computers came without a network card, and needed additional hardware to connect to a network.
You can share a USB modem internet to other computers on the network by simply creating a wireless network with the comp where the modem is connected and then connecting the other computers to the network via the wireless network that you created.
A Telecom network is a Telephone and Cable TV Network. A computer network involves computers.