(Adapted from eplain's intro.texi by Karl Berry)
  
The "Eplain" macro package expands on and extends the definitions in
plain TeX. 
  
Eplain is not intended to provide "generic" typesetting capabilities, as
do LaTeX (written by Leslie Lamport) or Texinfo (written by Richard
Stallman and others). Instead, it provides definitions that are intended
to be useful regardless of the high-level commands that you use when you
actually prepare your manuscript. 

For example, Eplain does not have a command `\section', which would
format section headings in an "appropriate" way, such as LaTeX's
`\section'. The philosophy of Eplain is that some people will always
need or want to go beyond the macro designer's idea of "appropriate".
Such canned macros are fine--as long as you are willing to accept the
resulting output. If you don't like the results, or if you are trying to
match a different format, you are out of luck. 

On the other hand, almost everyone would like capabilities such as
cross-referencing by labels, so that you don't have to put actual page
numbers in the manuscript. The author of Eplain is not aware of any
generally available macro packages that (1) do not force their
typographic style on an author, and yet (2) provide such capabilities

Besides such generic macros as cross-referencing, Eplain contains
another set of definitions: ones that change the conventions of plain
TeX's output. For example, math displays in TeX are, by default,
centered. If you want your displays to come out left-justified, you have
to plow through `The TeXbook' to find some way to do it, and then adapt
the code to your own needs. Eplain tries to take care of the messy
details of such things, while still leaving the detailed appearance of
the output up to you. 

Finally, numerous definitions turned out to be useful as Eplain was
developed. They are also documented in this manual, on the chance that
people writing other macros will be able to use them.