What is mean by in a network address?

That would depend on what you mean by address. If you mean the group of numbers e.g. 192.168.1.1 then this is the network address and it is the unique address of the computer or device upon a network - there are three classes of the types of IP (internet Protocol) addresses for use in internal and external networks, those with an address starting 192.168.x.x are three main classes of IPv4. Class C are for internal networks with less than 254 devices and always start 192.168.x.x Class B are for larger private networks and start 10.10.x.x and Class A are for internet connection and are issued to you by your ISP. There are reserved IP addresses e.g. 127.0.0.0 is the device's internal IP address.