When you want to work on a file in one of your filing cabinets, you may simply go to the right filing cabinet, open the right drawer, and pull out the file folder that you need.
Working with the computer, however, you must specify which filing cabinet and which drawer you want to open.
The computer insists that you provide the answers to its questions.
Which user are you?
Do you know the user password (if there is one)?
Which account do you want to use?
Do you know the account password (if there is one)?
Which group (in this account) do you want to use?
Do you know the group password (if there is one)?
Logging on is your way of answering these questions. Only after you have provided the correct answers does the computer permit you to use the file that you need.
Notice that the computer does not care which file you want to use. It simply opens the right cabinet (account) and the right drawer (group)—provided you have correctly answered all of the computer's questions.
