Client-server computing is a software engineering technique often used within distributed computing that allows two independent processes to exchange information, through a dedicated connection, following an established protocol.

Not understood? Try little simpler version. Client-server system is mainly two different processors that exchange information on common server. Unlike peer to peer system there is one server that stores the information and gives it only when the client provides specific identification like username.

Functions such as email exchange, web access and database access, are built on the client-server model. Take an example of banking service, Users accessing banking services from their computer (or mobile) use a web browser client to send a request to a web server at a bank. That program may send a request to a database server at another bank computer to retrieve the account information. The balance is returned to the bank database client, which in turn serves it back to the web browser client displaying the results to the user.

In the computer working on Windows, the server usually runs NetWare, Windows NT, or one of the Windows 2000 Server products. The server contains a list of usernames and passwords. Users cannot log on to the network unless they supply valid usernames and passwords to the server. Once logged on, users may access only those resources that the network administrator allows them to access.

Advantages of client-server system are;
(1) Content of server are secure, server allows client to use only that information that server wants.
(2) If a user happens to erase a
shared resource from the server, you can rely on the nightly backup. (It’s very difficult to back up a peer-to-peer network every night.)
(3) Client-server networks also tend to be much more stable.

Downsides of client-server system;
only downside to a client/server network is its cost. Servers can become very expensive.

Another type is peer-peer system which basically is a
computer network in which each computer in the network can act as a client or server for the other computers in the network, allowing shared access to files and peripherals without the need for a
central server.

Compared to client-server system peer-peer network has various drawbacks like;
-instance, a peer- to-peer network has no central server. Each workstation on the network shares its files equally with the others.
-It is not secure, anyone can access and do anything with files of other clients.

Use;
Peer-to-peer networks can be installed in homes or in very small businesses.
Client-server networks mostly used in large setups like Banks/corporate offices.