I don't know how this got started. Obviously, I hit some keys that caused
it but I have not seen this before and can't figure out how to clear it.

On the left side a my Word document, a vertical line has appeared near the
bottom and on the left side. And, when I type additional text there now, it
is underlined and is an orange/brown color. And, I discovered that, if I
move my cursor to another part of the document, above where this got
started, the vertical bar appears if a type any changes to that part of the
document and that new text is also in the colored and underlined font.

What is this, and how do I get rid of it?