The client/server model is a software architecture where applications are split into two parts: the server part that provides resources (data, operations, printer, storage, and so on) and the client part that uses the resources provided by the server. Traditionally, this architecture was used in the enterprise world but, with the boom in the internet, is still an actual topic. You can see a web application as a client/server application where the server part is the backend part of the application that is executed on a web server and the web navigator executes the client part of the application. SOA (short for Service-Oriented Architecture) is another example of a client/server architecture where the web services exposed are the server part and the different clients that consume them are the client part.
In a client/server...