Exactly what a service is and what it does depends very much on the particular application problem that it solves and the environment in which the service is deployed. It also depends on how accessible and available the service happens to be to potential clients that might make use of it in that deployment environment. Typically, service accessibility and availability depends on the network interfaces that it supports within its environment, which could be anything from a small local area network (LAN) to a global wide-area network (WAN). Services might support protocols limited to an intranet or support the widest possible available protocols on the Internet.
