Sometimes, you may find you need to type text ``as is'' without any
formatting or other operations being carried out on it. To achieve this,
enclose the material you wish to remain untouched by LaTeX between the
commands 
begin{verbatim} and
end{verbatim}. Note that
whatever is typed between these commands will be exactly reproduced and
will be unaffected by any LaTeX formatting, italicising, sectioning, etc.,
commands that may be contained in it. You would have to make sure for
example that the material was divided up into lines of appropriate length
for the final printed page. This verbatim mode is useful for such
things as program fragments, SGML examples, etc. The quality of text
produced looks like typewritten text as opposed to properly printed
text. We used verbatim mode for the example fragments of LaTeX commands
throughout this document (otherwise our examples would have been
interpreted as LaTeX commands and acted upon ...).
If you wish to quote a small amount of verbatim text, for example within a
sentence, then use the verb command. Here is an example:
Please note that
verb+begin{itemize}+
is a LaTeX command.
In the verb command, you must delimit material to be
printed verbatim by some character, such
as `+'. If you have more than one verb command on a text file
line then use a different delimiter pair for each occurrence.