The green dot is reputation - I'm not sure what the settings are for this forum but other forums I post on have it.

Everyone starts out on a "distinguished road" and this status changes as your post count increases to a certain level/number.

Each member can give good (green) and bad (red)reputation to any member for any given post.

To give someone reputation, click on the icon of the scales under that person's name (between the online/offline and "report bad post" symbols). A message box will appear asking if you approve or disapprove, and there is also an optional comments field.

You can check your reputation by clicking the "User CP" shortcut in the blue links bar. You can also use that link to view any threads you have subscribed to (if you subscribe to a thread you get e-mail notifications when a reply is posted)

Normally there is a number next to the green dot indicating the reputation power you have (number) if you give reputation to someone else. The more squares present, the more reputation that person has. The number increases when people give you reputation points. Members with light green squares have more power than those with dark green squares.

All new members start out as a "Junior Member" although in your personal settings there will be an option to create a custom title if you wish. This title changes as you reach each different level of posts (usually after each 100 posts).

Hope this info answers your questions

Amigo22