Note:  Personal workspaces are not accessible for users on the Free Business Edition. 

Your account's Personal Workspace is a great way to get started using the PBworks service.  Only your account has access to your personal workspace, and so you can feel free to experiment with the editor, create pages, and share select pages and files.  The personal workspace associated with each account is slightly different than a normal workspace, for instance there is no Members list where all users are explicitly listed, and you cannot make your personal workspace available to all users of the network to join. 

If you need a space where you need to build a team of users and have them all contribute pages and files, then you probably don't want to use your personal workspace for that kind of use.  The personal workspace is geared toward private usage, so you could use your personal workspace as a staging area, so that you can privately work on documents or store files privately, and then move them to more public workspaces within your network when the content is ready.

The PBworks Admin can also disable the personal workspace via the network settings.