A Group Space is a dedicated and centralized place in the community for members to collaborate on common projects or topics. Consisting of a widget-based homepage and a collection of applications that are specific to that Group Space, they can have their own wiki, documents, blogs and forums etc. You can even add additional pages to a Group Space to further expand it's content.

A Page is a blank canvas which is used to expand your site and give custom areas to a community. Adding a page results in the ability to drag widgets into place, creating a layout which is unique to the pages purpose. A contact page if created could house a list of members using the members widget, you would refine this widget to show only admins using it's settings. You could use the blog widget to display your technical notices blog channel on the contact page so members are aware of issues before contacting. Of course the need for custom text and information on a page is necessary and possible using our HTML widget which allows for you to place custom text and images on a page.

To sum up the difference, I would say that Group Spaces are a collaboration tool and pages are used to expand your communities depth.

If you have questions like this in the future, please feel free to search our support site with the term to get more information.
More on Group Spaces: http://support.igloosoftware.com/wiki/groupspaces
More on Pages: http://support.igloosoftware.com/wiki/pages