The keyboard.xml file controls how Kodi reacts to keypresses, that is it determines what action is mapped to what keypress. There are two main reasons for modifying keyboard.xml:

1. You want to change the standard key mappings because of a personal preference
2. You are configuring a Media Center remote control that sends keypresses

You can edit keyboard.xml using any text editor such as Notepad++ in Windows or gedit/nano in Linux. The location where the file should be located after creation is in userdata

There is a more detailed discussion of the keyboard.xml file. This article is focussed on the gory details of editing it.

Keymap Editor is a GUI for configuring mappings for remotes, keyboard and other inputs supported by xbmc. Note: existing user defined key mappings will be removed.