The underscore character _ is ordinarily used in TeX to indicate a
subscript in maths mode; if you type _ in the course of ordinary
text, TeX will complain. If you're writing a document which will
contain a large number of underscore characters, the prospect of
typing \_ (or, worse, \textunderscore) for every one of them
will daunt most ordinary people.
Moderately skilled macro programmers can readily generate a quick hack
to permit typing _ to mean 'text underscore'. However, the code
is somewhat tricky, and more importantly there are significant
points where it's easy to get it wrong. There is therefore a package
underscore which provides a general solution to this
requirement.
There is a problem, though: OT1 text fonts don't contain an
underscore character, unless they're in the typewriter version of the
encoding (used by fixed-width fonts such as cmtt). So either
you must ensure that your underscore characters only occur in text set
in a typewriter font, or you must use a fuller encoding, such as
T1, which has an underscore character in every font.
If the requirement is only for occasional uses of underscores, it may be acceptable to use the following construct:
\def\us{\char`\_}
...
\texttt{create\us process}
The construction isn't in the least robust (in the normal English
sense of the word), but it is robust under expansion (i.e., the
LaTeX sense of the word); so use it with care, but don't worry
about section headings and the like.