If you have a number of computers in an office and want to be able to quickly share files and documents then you may need to install a network. There are a number of ways of networking computers and some companies opt for an exchange server. This is a server that will most likely be situated in the office building. The space on the server will be able to be accessed by anyone on the network. Depending on what user privileges they have been given, they may be able to read, write, edit and save documents on to the server and access ones that others have created. This can save time and also allow all work to be backed up from one server rather than having to back up multiple computers at the end of the day.
If you do use an exchange server then you will need to ensure that it is backed up as should you lose the information, it may not be copied on to local machines.