Actually in distributed databases when a user wants to access data and if that particular data does not exist on user computer then it is the responsibility of DBMS to provide the data from any other computer where it exists. User does not know about this thing as from where data is coming.
Network transparency also means roaming transparency and it gives the freedom of entering query from any workstation to a user. So a user does not know from where the results of query are coming as results may be coming from user workstation or any other workstation. Here the term roaming means that if a user moves from one place to other then all other users does not know about this.
If a user enter a query to access data and query does not find the data in his/her computer then query goes to the other places and user does not know about this. It means that one any thing moves from one place to other it does not affect on the processing of the data as well as on the whole network.