The icons you see next to someone's name on a class list indicate profile information they've posted (photos, notes, story, location), if they're in a yearbook on the site, or if they've added something to their Bucket List. Simply hover over an icon to see what it means. An orange star on an icon means the content is new.
Keep in mind that you can use filters to show people who have profile info posted by choosing the Has yearbook, photos, more option from the drop-down menu at the top right of the list, next to where it says Class List.