A client-server network is a model whereby multiple clients e.g. people using computers, connect to one central server.
Each client sends unique data requests to the central server for processing. Once processed, the central server sends responses back to each client.
In this model, there will always be a dependency on the central server.
If there is an issue with the central server, the entire system could be impacted.
And if one gains control of the central server, they will have access to entire system