Text Codes are used in the Show Text event command. They are used to display things that text normally can't produce on its own, such as colors, get the name of a specific actor, change icons, and more.
RPG Maker MZ already comes with text codes of its own:
Here is a list of Text Codes that you may use.
== Message Core (VisuStella MZ)
The following 2 pages are in this category, out of 2 total.