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 L A TEX language is described in the book L A TEX - A Document Preparation System. L A TEX is a TEX macro package, not a modification to the TEX source program, so all the capabilities described in tex(1) are present.
The L A TEX macros encourage writers to think about the content of their documents, rather than the form. The ideal, very difficult to realize, 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.
The primary source of documentation for L A TEX is the L A TEX manual referenced below, and the local guide in the file local-guide.tex or local.tex or some such.
elatex is the e-X extended mode version of L A TEX format.
lambda is the Omega version of the L A TEX format.
pdflatex is the pdfTEX version of the L A TEX format.