Proxima Nova is a sans-serif font. It goes well with Helvetica Neue, Lucida Grande, Adobe Garamond, Georgia, Atrament, Skolar, Century School, Adelle, Futura PT and Didot. If you're thinking about using Proxima Nova then try 24px for headers. Give 16px a shot for content.
People commonly tag it as design, agency, tech, modern, portfolio, app, sans serif, writing, photo and magazine. You can get it from Fontdeck, Fonts.com, Fontshop, Fontspring, MyFonts, Typekit and YouWorkForThem.