The term “centralized” pertains to an organizational structure wherein a select number of nodes holds control of the whole network. Centralized systems are used by clients and server architecture with the nodes being directly connected to the central server.
The centralized system is the type of system that is most commonly used in many organizations in which clients send a request to a company server and in turn receive a response from it.
A good example of a centralized system would be Wikipedia. When one lodges a search through the Wikipedia search bar, this is sent as a request to the site’s servers which respond with links to articles based on relevance. Within this context, the client who had entered the search keywords are aptly called the client node, while the Wikipedia servers are part of the central server.