英语语法.....

这个句子里ing形式作状语，表示伴随状况。

单纯说为什么表伴随不太好解释，不过可以看看ing在句中可以表示的意思，能帮助你更好的理解ing的成分和作用。
ing可以表示时间、原因、结果、条件、让步、行为方式、伴随状况等。如:
Being a teacher, you should help your students in every way.(原因)
He died from a sudden traffic accident, leaving the experiment half-done (so that he left the experiment half-done).(结果)
Seeing my parents waving in the crowd, I went running to them.(时间;方式)
The students entered the classroom, following their English teacher.(伴随)
Listening to English every day (If you listen to English every day), you’ll learn it well step by step. (条件)