Flickr: I've created a Flickr account and uploaded a photo. The pic above is from Washington D.C. when I attended the National Council of Teacher of Mathematics National Convention last April. I changed all my privacy settings...creeps me out a bit that photos I post can be searched, downloaded etc. That's me and my digital immigrant-ness expressing itself!
Tagging: I've tagged photos in Facebook before and I imagine the process works much the same here, although on Flickr you can tag a photo to show up and be viewed by a specific "group" of users and also that one photo can accomodate 75 tags.
Groups: is a group of users you are a member of, like all the library groups. What a great way to share what's going on around the world with folks that have similar interests...like library functions, programs, etc.
Ann