Network drives are a location to save your files on a file server at Dawson. They are backed up every night. The Home drive or H: is your home directory: the data that you save here can only be seen by you. The Shared drives, S: and R:, are used by faculty to share data with students (S:) or to share data between employees (R:).
All your data should be stored on shared drives, as opposed to local (e.g. C: drive) to take advantage of the nightly backup. In addition this will make it available for you from other workstations or even from home (see articles about Remote Access).