Courier is a serif font. It goes well with Proxima Nova, FF Tisa Web Pro, Helvetica, FF Meta Web Pro, Times, Benton Sans, Chivo, Lucida Grande and Consolas. If you're thinking about using Courier then try 18px for headers. Give 18px a shot for content.
People commonly tag it as modern, newspaper, stark, mono, responsive and vintage. You can get it from Fonts.com, Fontspring, MyFonts, Typekit and YouWorkForThem.