is the name used to refer to the default set of ''macros'' which are always present on all systems (and it is the default preloaded format for tex executable). They were written by Knuth himself, and provide the basic to start using (since "raw" is not ready-to-use for documents creation). Often when one says simply " document", s/he means s/he is using the macros, even though nowadays the success of the complex feature-full macros package creates a little bit of confusion and a lot of people, ignoring that is just one of possible macro packages for , think that is and viceversa.

Extension to the exists, like eplain().

Even though is nowadays almost a typesetting "standard" when using a system, is still usable and used.