What is a helping verb, then?

那么究竟什么是助动词呢？

Now that you've seen this list, do you understand what a helping verb is?

现在你看到这个助动词表了，你知道什么是助动词了么？

Long, long ago, when I was in junior high (and you can tell it was a long time ago because we actually called it junior high back then), I had a teacher who did not know what a helping verb was.

很久很久以前，当我还是个初中生的时候，有一位老师不知道什么是助动词，但他却得教我们这个知识。