Type in a number and press GENERATE to see what words it translates to, according to the standard telephone keypad. For example, 866 is "TOM", as well as a number of other, mostly nonsensical, three-letter combinations.
With the dictionary option, you will also learn what words the number is hidden inside. The dictionary used is "2of12" of Alan Beale.
You need an up-to-date JRE (Java Runtime Environment) to use this tool.