Unicode, UTF-8 and multilingual text: An introduction - Overleaf Blog
▻https://www.overleaf.com/blog/617-unicode-utf-8-and-multilingual-text-an-introduction
Modern TeX engines, i.e., XeTeX and LuaTeX, have evolved from Knuth’s original TeX engine largely due to the need to keep pace with developments in the technology landscape, particularly Unicode (for text) and OpenType (for fonts). Today, through the use of packages such as fontspec and unicode-math, LaTeX users can access extremely sophisticated typesetting capabilities provided by OpenType fonts—including advanced multilingual typesetting and OpenType-based mathematical typesetting (pioneered by Microsoft).
However, to get the most out of using OpenType fonts with XeTeX/LuaTeX, it can be helpful to become familiar with a number of background topics/concepts—especially for troubleshooting problems or to pave the way for more advanced/complex work. For example, you might read about the XeTeX and LuaTeX engines using “UTF-8 input” or that they are “Unicode aware”, and further reading on OpenType fonts might discuss or mention topics such as “Unicode encoding”, OpenType “font features”, “glyphs”, “glyph IDs”, “glyph names” and so forth. Our objective is to provide an introduction to these terms/topics and piece together a basic framework to show how they are related and, hopefully, provide support for further work or problem-solving.
The topics we aim to cover fall fairly neatly into two main areas: Unicode which, in effect, inhabits the world of text/characters and text encoding and OpenType whose world is one of fonts and glyphs; but, of course, those two worlds are interconnected and there is some crossover, even in this first article.