Every LAN may or may not be with WAN but every WAN is with LAN.
A computer network simply consist of set of machines and other devices like routers,smart devices etc. They are all able to communicate with each other in computer language,also they understand eachother very well and transmit data.
A LAN (Local Area Network),is small network as compare to WAN (Wide Area Network) ,LAN works within small geographic portions like intercollege, school, home ,etc. LAN is private network,so an outside regulatory body never controls it.Here you can use the same software over the network instead of purchasing the licensed software for each client in the network.
While WAN network is widely spread like scientific purposes ,government etc.They can communicate data of widely spread networks in big corporations and also exchange data.WAN generally consist of many small networks (LAN).WAN is not private it can be used by all users,hence all can access to latest files. Any organization can form its global integrated network using WAN.
Reasons for Every LAN may or may not be with WAN,but Every WAN will be with LAN.
WAN have a large capacity of connecting a large number of computers over a large area having many LANs. They facilitate the sharing of regional resourses. They provide uplinks for connecting LANs to the internet. And to cover wide geographic area for communication we can not use LANs so we used a Wide Network Area(WAN) consisting different Small Area Networks(LAN). Devices on LAN often use the LAN’s infrastructure to connect public internet(WAN), but can often communicate with eachother directly through LAN more quickly. For instance,it is not compulsory to send file to public network(WAN)for getting the same on LAN.
Also LAN is a private network ,so to access new data publically we used WAN.WANs are used to connect LANs and othertypes of networks together so that users and computers in one location can communicate with users and computers in other locations.
For example,
1.A school network could be connected to internet,and within school network all machines in school are interconnected which is nothing but a LAN and internet is a WAN.
2.Computers in one SBI are interconnected which is definitely a LAN and this whole network is connected to all over SBI banks in India which is a WAN.
And these days the general consensus is that a WAN is a geographically dispersed collection of LANs.
3.4G network that services populated areas across a region or country(WAN) and network towers in villages or town(LAN).
