The core Google+ features are:
Circles: A method of assigning people to different micro-networks and then sharing information with only them
Hangouts: Video chats where people can get together and catchup
Huddles: Ongoing IM conversations across groups
Sparks: Search for content by your friends and share your own content
Google plus is still being tested right now. After the testing period, many invites will be sent out. Sign up for invitation here
Watch:
Folks are already developing a collaborative Google Doc for tips and tricks with Google +
Read more commentary from PC World on Google+ and privacy.
See also: thoughtful post by Ryan Bretag: He argues that rather than trying to "school-ify" Facebook, Google + could fit the bill for classroom learning commons.