MS word question

I have a document i am working on, but its an older document and when i delete something its still there but turns red and has a line going through it, and there are vertical lines on the left side that appear when i type a new line.
Is this some sort of editing mode?
How can i adjust or get rid of it?

That’s called “change tracking”. I don’t use MS Word, but these instructions appear to be correct:

excellent, thanks