For instance, in this Texinfo manual, 
if I want to insert a @@ or a @{
I have to ``escape'' them to make them appear literally
since they have a special meaning in Texinfo.  
The same holds, e.g., 
for @code{<}, @code{>} or @code{&} in HTML.  
If you use source-highlight,
it will take care of this, automatically for you.