The pathname is the route that a computer takes in locating a file (or other type of object). By giving the computer a pathname to open or save a file, you are basically telling it where to go. "Path" specifies the location of a file within a computer's directory. It also refers to the link between two machines.
A pathname in DOS will specify the drive, directory, subdirectory (if any) and name of the file. It could look something like this:
C:\PROGRAMS\PAPERS\SHAKESPEARE\OTHELLO.DOC