Transliteration is a way to type phonetic english to spell out sounds of words in a foreign language, and have the english characters translated into the correct characters from another language.
Google has great transliteration support in gmail and it's really easy to turn on.
Mail Settings, in
General the top grouping is
Language. Select the
Show All language options option, which will reveal the transliteration settings
After doing that you will have a checkbox to enable transliteration
Now when composing new messages in rich-text format, there is an icon to turn on transliteration.