In case you are confused:
Webpages have to be displayed on lots of different computers, and they don’t all have the same fonts installed. Generally speaking, Windows will have one set, Mac another, Ubuntu another etc. So you can specify a font in a webpage, but if it doesn’t exist it’ll just use the default, with crap results.
So you specify a list in terms of preference, which is what lemonysam is talking about. And possibly the reason why Stoner is seeing it differently to you – he’s probably on his Chromebook and they could have different fonts.
Any system though will have a default font and a default monospace font. Monospace being one where all the letters are the same width. It looks crude but it’s important for such things as code where the spacing is important.