tough to say as there are millions upon millions of apps each with their own notification icon. so even if you had a screenshot(which i would recommending posting....if you can get it), it would be very difficult to get an answer. unless it is a popular app like facebook or youtube, most of these questions go unanswered.
the easiest way is to go into the phone's settings under notifications to find out.....just ask your friend to do this and you will know.