Within each group in the Intranet, you can create different types of content. Each type serves a different purpose, so choose wisely.
A "collaboration" is for content that can be edited by all members of the group. It's useful for works in progress, like the page you are reading now.
A "group event" is designed for sharing future event information with your other group members. Typical uses include meeting anouncements and important future deadlines (e.g. application deadlines). This content will be displayed on the group's Upcoming Events and Calendar pages, and also cleverly aggregated on the site-wide Upcoming Events and Calendar pages, but only visible to those who are in your group.
A "document" is a placeholder to describe and upload a word file or PDF that you want others to read, and possibly provide comments on.
A "message" is a simple piece of content that is sent by email to all your group members immediately. Use it to get the attention of your group members for simple messages. The message will be archived on the site.
A "webform" is a kind of "survey monkey" for your group. Use it when you want to ask a series of structured questions from your members. The answers will be stored on the site for your retrieval as a spreadsheet. This kind of content takes a while to understand, feel free to ask for help.