gvim - What is the vertical gray part of the diagram in vim ui?

Question

As shown in the attached picture, there are two split windows in the picture. The one on the right appears when taglist is opened.
I specially added set nu for comparison.
What is the gray-white vertical bar on the far left side of the taglist window and how to control it?

Answer 1

That one is called sign column, you can look at the help in vim to learn more about it :help signs

If you want to get rid of it, I think the easiest way is: :sign unplace *, give it a try.