The FontChain component provides an easy way to use "Fallback" fonts for a main font, usually in the event that the main font does not contain certain Unicode characters. Any place where a StaticFont can be used, a FontChain can be used.
The MainFont defines which font will be primarily used for the text. For any characters of a text that do not exist in the main font, all the FallbackFonts will be searched through, in order, to find a matching character. Only if all fallback fonts do not contain the character will a "true fallback" of a box will appear.