kbd elementHTMLElement.The kbd element represents user input
  (typically keyboard input, although it may also be used to represent
  other input, such as voice commands).
When the kbd element is nested inside a
  samp element, it represents the input as it was echoed
  by the system.
When the kbd element contains a
  samp element, it represents input based on system
  output, for example invoking a menu item.
When the kbd element is nested inside another
  kbd element, it represents an actual key or other
  single unit of input as appropriate for the input mechanism.
Here the kbd element is used to indicate keys to press:
<p>To make George eat an apple, press <kbd><kbd>Shift</kbd>+<kbd>F3</kbd></kbd></p>
In this second example, the user is told to pick a particular
   menu item. The outer kbd element marks up a block of
   input, with the inner kbd elements representing each
   individual step of the input, and the samp elements
   inside them indicating that the steps are input based on something
   being displayed by the system, in this case menu labels:
<p>To make George eat an apple, select
    <kbd><kbd><samp>File</samp></kbd>|<kbd><samp>Eat Apple...</samp></kbd></kbd>
</p>
   Such precision isn't necessary; the following is equally fine:
<p>To make George eat an apple, select <kbd>File | Eat Apple...</kbd></p>