Doc. improvements from Chris

I've re-written the part about catcodes entirely.

base/doc/usrguide.tex

@@ -804,45 +804,49 @@ \subsection{Using the verbatim argument types}
 
 When grabbing a \texttt{v}-type argument, \LaTeX{} first uses the kernel
 command \cs{dospecials} to turn off the \enquote{special} nature of characters.
-It then makes both spaces and tabs \enquote{active}, so they can be given a
+It then makes both spaces and tabs \enquote{active}, so that they can be given a
 custom definition. Any other characters are grabbed as-is: this means that if
 any characters have been made \enquote{special} and are not listed in
 \cs{dospecials}, an error will arise (see below).
 
-Characters are grabbed between two identical delimiters: in contrast to \cs{verb}, the
-characters \texttt{\textbackslash}, |{|, |}| and |%| \emph{cannot be used}. If
+The characters that are grabbed as the argument are all those between two identical:
+in contrast to \cs{verb}, the
+characters \texttt{\textbackslash}, |{|, |}| and |%| \emph{cannot} be used as the
+delimiter character. If
 any of the grabbed tokens have \enquote{special} meaning, an error will be
 issued.
 
-For the \texttt{+v}-type argument, which allows line breaks in input,
-newline characters are converted into \cs{obeyedline} commands. This means that
-the grabbed tokens can be used directly in typesetting, while a local
+For the \texttt{+v}-type argument, which allows line breaks within the argument,
+newline characters are converted into \cs{obeyedline} commands. The standard
+definition of \cs{obeyedline} is simple |\par|, thus allowing the grabbed tokens
+to be used directly in typesetting. A local
 redefinition of \cs{obeyedline} can be used to achieve other outputs. For
 example, to retain blank lines whilst typesetting, one could use
 \begin{verbatim}
 \renewcommand*\obeyedline{\mbox{}\par}
 \end{verbatim}
-along with other setting that may be appropriate (e.g., using a monospaced
-font).
+More information about using these arguments in typesetting is in the following
+subsection. 
 
 Some additional details that may be useful for those with more \TeX{}
-knowledge: do not worry if this does not make sense to you! Grabbed tokens are
-all stored as either active or \enquote{other}: spaces, tabs and non-ASCII
-codepoints in $8$-bit engines are active, everything else is detokenized. As
+knowledge: do not worry if this does not make sense to you! Spaces and tabs are
+stored as active characters. In Unicode engines, all other characters are of
+type \enquote{other}. In $8$-bit engines, the ASCII characters other than tab
+and space are of type \enquote{other}, and non-ASCII characters are active. As
 such, token-based comparisons are likely to fail unless set up properly.
 
 \subsection{Typesetting verbatim-like material}
 
-In contrast to \cs{verb}, the \texttt{v}-type argument is only about
+In contrast to \cs{verb}, the \texttt{(+)v}-type argument is only about
 \emph{grabbing} the argument, not \emph{typesetting} it. As such, features that
 users often associate with \enquote{verbatim} are not automatically activated,
-e.g., a monospaced font. Material grabbed by the \texttt{v}-type argument does
+e.g., selecting a monospaced font. Material grabbed by the \texttt{v}-type argument does
 not automatically suppress ligatures: with modern \TeX{} engines, this largely
 can be done without the token manipulation which \cs{verb} uses. (In \cs{verb},
 ligatures are suppressed by making characters active and inserting a zero-width
 kern before the character itself.)
 
-The \cs{verb} command also selects a monotype font: this is not intrinsic
+The \cs{verb} command also selects a monospaced font: this is not intrinsic
 to verbatim material, so will need to be set up using for example \cs{ttfamily}.
 Similarly, the \texttt{verbatim} environment sets up the meaning of \cs{par}
 suitable for breaking lines.