Content Delivery Network or CDN, as the name aptly suggests is a network of servers across multiple geographic locations. The purpose of such a network is swift delivery of data to the end users from servers closest to their location.
The working of Content Delivery Network is based on the fact that when the end user tries to access the data from a server quite distant from its location, it can sometimes experience lag or time delay in transmission. This is because everytime a request is sent to a server, it has to do multiple hops before it reaches the destination. For instance, if a user in Texas tries to access a server in Washington DC, the data has to be transmitted along a long distance.
Under CDN, the main server is connected to a network of servers spread across multiple geographic regions. The data is replicated to all the servers so that when the user tries to access the data it is directed to the nearest server. The data that is stored on the main server is constantly replicated to all the CDN servers which ensures a faster response and also data replication in case the data is lost on the main server. Content Delivery Networks are useful when swift streaming of data is required.