$HOME
(same as ~/)

This is your home directory. It is the only place to store data which you wish to keep. Your home directory is saved by the backup system every night, but you have a limited amount which can be saved here. (To see how much you have saved and how much you are allowed to save, use the quota(1M) command. For more information, see below.)

/scratch

Scratch uses the data area which remains on the hard disk of the local machine after after all other necessary items are installed on the disk. It is the right place to store large quantities of data which have been downloaded from the Web, or temporary files which are produced during the solution of a laboratory exercise.

The scratch area is not backed up, and its contents will be erased automatically when it begins to become full.

/pub/anarchy

This area may be called a shared scratch. Use this area when you need to save something which should be accessible from a different computer from that which you are using right now; for example, if you want to install a somewhat larger program which does not fit in your home directory.

/tmp
/var/tmp

These are the wrong places to save large quantities of temporary data. This space is used by applications to save temporary data; if it becomes full these applications will function poorly or not at all. Therefore, do not use this area for other purposes than quick storage of smaller amounts of temporary data. This directory is emptied with each boot of the machine and older files are purged automatically while the system is running.