Encoding special chars
----------------------

The LaTeX Info pages lists under "2.18 Special Characters"

  The following characters play a special role in LaTeX and are called
  "special printing characters", or simply "special characters".

                            # $ % & ~ _ ^ \\ { }

The special chars verbatim::

                            # $ % & ~ _ ^ \ { }

However also *square brackets* [] need special care. 

   \item and all the other commands with optional arguments check
   if the token right after the macro name is an opening bracket.
   In that case the contents between that bracket and the following
   closing bracket on the same grouping level are taken as the
   optional argument. What makes this unintuitive is the fact that
   the square brackets aren't grouping characters themselves, so in
   your last example \item[[...]] the optional argument consists of
   [... (without the closing bracket).

Compare the items in the following lists:

* simple item
* [bracketed] item

simple
  description term

[bracketed]
  description term

The OT1 font-encoding has different characters for the less-than,
greater-than and bar, < | >, except for typewriter font `cmtt`::

   < | >