Site friends are people who have joined the site with friend connect.

1. Your basic GFC profile info: image, name and text. NOTE: if you "use a different profile" e.g. connect to your Google profile, then you name becomes a direct link to the Google profile page.
2. Your activity you have chosen to show on GFC sites.
Note: that you have to choose to activate this under "settings" for each site. You can see in the example how Robert has made friends with someone on a different GFC enabled site else ware. His activity on that site is shown here, because he has opted to show his activity on that site.
When this screenshot was taken, the profile was viewed by the logged in profile owner: you should note that when logged in, each "activity" can be removed from your activity stream by clicking the small bin or trash icon. This removes that activity from your GFC activity stream, but does not remove the activity (e.g. a comment) on the site where it was made.
3. Links you have added to your GFC profile. If you add more than five links they are shown on a new profile page from the "More >" link on the right of the links section of your profile.
4. Sites you have joined with GFC. You can choose not to show a site you have joined from the settings link when logged in on that site.
5. Friends: this is a term which some people have a problem with. You should think of "friends" as a contact you have met on a site rather than a "buddy". If you have made "friends" with someone then you will "see" them listed as a friend on other GFC sites you both join. Being friends will also be useful to cut down the "noise" on a busy comment wall gadget, as you can click to "show only friends" comments in canvas (full gadget view) mode.