In simple terms, a network is a set/series of interconnected devices. What do we really mean by interconnected devices? Well, the devices that can talk one another or control one another. In a computer lab, there might be set of computers connected together; those computers might have an internet connection, which means that those computers are connected with some WiFi device through router. The administrator of your computer lab has an access to each and every computer via his computer. There might be a printer attached with at least one computer of class computer lab. All of these things combined together to form a network in terms of the class computer lab. Just keep the simple definition of a network mentioned-above in your mind, and apply it in your class computer lab.