Public folders are used in Exchange to store various forms of information. Access to public folders can be restricted to individuals and groups and are commonly used for:

Shared communication
This includes discussion through message posts, shared e-mails, contacts, and group calendars.

Shared content management
Similar to file shares, public folders can be used to hold content such as documentation and are good for content sharing. However, if you have collaboration requirements, you should review other solutions and technologies.

If offline storage of information is required, public folders are an ideal repository.