Green call icon on the top middle of Apple Watch.

Hello

I do not know what is the benefits of the green call icon that appear in the top middle of my apple watch ..

When I received a new call .. the iPhone and Watch ringing ,, I answer the call from my iPhone and I finished it from iPhone, When I look to my watch the green icon appear and I can not dismiss it. When I tap on It, It calling the number direct :( !!!

Can any one clear !

Thanks in advance.