Fonts are a resource that allow you to embed a certain font family and size into your game. With programs like Microsoft Word, you can select different fonts to change how the text of the document is rendered. The problem with this is that the font files used by these programs are often large (several megabytes) and also in what's called a vector format. The fonts are also sometimes proprietary and owned by a company, like Microsoft, who do not allow you to use them in your own software without a license. What the font resource does is converts the font that you choose into a texture with only the glyphs (aka characters) you actually intend to use and then stores this font image in your project so that it will still work on computers that do not have the font installed.