Need Help getting rid of Quill Pen symbol.

So this feather/quill pen looking symbol is ruining my life. lol. Not sure what I did to activate it, and not sure how to get rid of it. Tried googling and youtube and came up with nothing. Can't find it in manual because I have no idea what it's called.
It rewrites over what I already written in any line of code. This is effecting all my objects as well. I basically have to rewrite a lot of lines twice now. How do I get rid of it? Thanks.