You're reading text right now. Characters representing primarily letters and numbers, usually arranged to present a message.
Text presents special issues to game developers because one has to account for both visibility and readability. It refers to text that is meant to be read by the player, not by in-game entities. Can be used in menus, to represent dialogue, or as parts of the world like in signs.
Questions with this tag deal with how to store, manage, and render text in the game world.