What is `plan` for users?

Put some text into the file ~/.plan and try finger again:

$ finger yeti                                      
Login: yeti                             Name: yeti
Directory: /arpa/tz/y/yeti              Shell: /bin/ksh
On since Wed Apr  2 15:24 (UTC) on pts/149
Mail last read Mon Mar 31 11:08 2014 (UTC)
No Plan.
$ echo Mwhuaaaaahahahahahahahahahaaaa... > ~/.plan
$ finger yeti                                      
Login: yeti                             Name: yeti
Directory: /arpa/tz/y/yeti              Shell: /bin/ksh
On since Wed Apr  2 15:24 (UTC) on pts/149
Mail last read Mon Mar 31 11:08 2014 (UTC)
Plan: Mwhuaaaaahahahahahahahahahaaaa...

It's an informative feature of the UNIX/LINUX system allowing a user to give an idea as to what he is working on, or in the middle of ...

Much like the .project, which tells you what project he is currently working on, the .plan tells of his process, or intent, or whatever he or she may want to convey, with the .plan file in their home directory.

When I create a new user, I create a .project file, stating their office project, and the .plan file, with the words something to the effect ...

No plan given at this time ... update ~/.plan to update this information.

(this is automatically added by the user account script I created)