README.md: Update intro

README.md

@@ -5,6 +5,8 @@ bindings with a common prefix - a Hydra.
 
 ![hydra](http://oremacs.com/download/Hydra.jpg)
 
+## Description for Poets
+
 Once you summon the Hydra through the prefixed binding (the body + any one head), all heads can be
 called in succession with only a short extension.
 
@@ -13,6 +15,20 @@ Hercules, besides vanquishing the Hydra, will still serve his original purpose,
 command.  This makes the Hydra very seamless, it's like a minor mode that disables itself
 auto-magically.
 
+## Description for Pragmatics
+
+Imagine that you have bound <kbd>C-c j</kbd> and <kbd>C-c k</kbd> in your
+config.  You want to call <kbd>C-c j</kbd> and <kbd>C-c k</kbd> in some
+(arbitrary) sequence. Hydra allows you to:
+
+- Bind your functions in a way that pressing <kbd>C-c jjkk3j5k</kbd> is
+equivalent to pressing <kbd>C-c j C-c j C-c k C-c k M-3 C-c j M-5 C-c
+k</kbd>. Any key other than <kbd>j</kbd> or <kbd>k</kbd> exits this state.
+
+- Assign a custom hint to this group of functions, so that you know immediately
+after pressing <kbd>C-c</kbd> that you can follow up with <kbd>j</kbd> or
+<kbd>k</kbd>.
+
 If you want to quickly understand the concept, see [the video demo](https://www.youtube.com/watch?v=_qZliI1BKzI).
 
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