This manual page is not meant to be exhaustive. The complete documentation for this version of TEX can be found in the info file or manual Web2C: A TeX implementation.
The AMSTEX language is described in the book The Joy of TEX. AMSTEX is a TEX macro package, not a modification to the TEX source program, so all the capabilities described in tex(1) are present.
The AMSTEX macros encourage writers to think about the content of their documents, rather than the form. The ideal, not always realized, is to have no formatting commands (like ``switch to italic or ``skip 2 picas) in the document at all; instead, everything is done by specific markup instructions: ``emphasize, ``start a section.
AMSTEX is the official typesetting system of the American Mathematical Society, and nearly all of its publications are typeset using AMSTEX. The online version of AMS Math Reviews uses AMSTEX input syntax for display of mathematical material. AMS authors can provide editors with computer-readable AMSTEX files.
Documentation for AMSTEX, typesettable by TEX.