Direct Traffic is depicted by green. So this is the second best thing that could happen to your website
Referring Sites are the website which are referred by other websites like traffic exchange websites. The more traffic you are getting from these websites the more damage you are doing to your websites or blog. And I am not talking about good referring websites like Social media and search engines. Search engines have a way to identify traffic exchange websites and they know you are generating fake traffic.
The Best Kind of traffic is from Search Engines. It is clearly marked with Blue part
The yellow portion which you see in the circle is of traffic sources which are undetermined. This again is a bad thing and search engines feel that your traffic sources are suspicious that is why you want to hide them.