Once you have created the folder you can grant users or groups access to that folder. For example you may have a central contacts folder that is the master address list for your organization and so you many not wish all users to have delete access for example. So, you can give full control to the contact list manager and read access to everyone else.
You can create a calendar for a shared resource such as a conference room, and give people the appropriate access rights. That way all appropriate users can book time out and you can manage who can do what using the access rights.