A computer can be a client or a server or both at the same time.
client- a computer accessing resources hosted by another computer, the server. Resources could be documents, printers, scanners etc.
server- a computer hosting resources to be shared across the network, like documents, printers etc.
Examples of servers:
- DNS server - maps web addresses to IP addresses
- Router - Device that connects two different networks
- Firewall - a computer or software package, which needs specific hardware, monitoring and protecting the network traffic of a computer or computer network. It decides which computers get access to the network or computer based on a set of rules. The difference between firewall and antivirus is that the firewall is used for the network.
- E-mail server - Maps e-mail addresses to IP addresses.