Network: Is a connection between people who live, work and go to school together. By registering for a work network, you expand your Facebook universe. The site offers co-workers at supported companies the chance to network both for work and fun.
Moreover, I found the differences between groups and pages in pollenizer.com page. The article is written by Bree Clare.
Groups: Are for members of groups to connect, share and even collaborate on a given topic or idea. You can send private messages and there are no applications. Respecting to membership restrictions, the groups can be open, close or secret.
Pages: Allow entities, such as public figures and organizations, to broadcast information to their fans. You can send messages, as “Updates”. As a applications, you can be added to page.
References:
-The reference about networks: Anonymous contributor. (2010) How to Join A Work Network On Facebook in eHow, from http://www.ehow.com/how_2031194_join-work-network.html
-The reference about groups and pages: Fleur Fletcher. (2010, April 20th) Facebook: Groups Vs. Pages. Retrieved April, from http://www.pollenizer.com/facebook-groups-vs-page
