This is probably a very stupid question, but I'm not too technologically inclined. I see often when someone 's post is containing an excerpt from a book or an article, recommended changes, etc. it's often on a yellow surface. Someone has even edited my post containing an excerpt from my own book to have a yellow background. I didn't mind it, but it furthered my curiosity as to how one does this.
Simply prepend your text with a greater-than sign.
> This is quoted text
This is quoted text
Many more details available when clicking the question mark in the upper right of the post editor, including a link to the full Markdown Editing Help page.