Which term describes a computer that provides services or resources to client systems?

The term that describes a computer that provides services or resources to client systems is "server." In a client-server model, the server's primary role is to manage and provide access to resources such as files, applications, or data over a network. When a client system requests a service, the server processes that request and responds accordingly, whether that means delivering data, hosting applications, or managing requests for information.

In network architecture, servers are typically more powerful than clients and are configured to handle multiple requests from various clients simultaneously. This infrastructure underpins much of today's internet services, where servers respond to numerous client requests, facilitating activities like web browsing, file sharing, and email communication.

The other options refer to different roles in network communication. Clients are the devices that request services; routers direct traffic between different networks; and hubs serve as basic networking devices used to connect multiple devices in a network without filtering traffic. Each of these has distinct functions that do not involve the provision of services or resources in the same way that servers do.