There are 2 basic bullets, which symbolize kind of a "country code":

Balls a ball links to: mainly american/canadien sites but stands also for worldwide links ... ... besides links exclusive to Germnay/Europe

Diamonds a diamond links to: mainly german sites - also often just in german but stands also for european links

BTW:
If you are clicking on the bullet, the link will be opened in the same browser window!
In case you are clicking on the text behind the bullet a new browser window will be opened (as long as it is an external link and not a link to one of my own pages) !