Courier is a serif font. It goes well with Proxima Nova, Times, Chivo, Helvetica, FF Meta Web Pro, FF Tisa Web Pro, Benton Sans, Consolas and Lucida Grande. 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 Adobe Fonts, Fonts.com, Fontspring, MyFonts, Typekit and YouWorkForThem.