The katakana
syllabary is mainly used for writing
borrowed
foreign words. The
Japanese have been using words from other
languages for a while now, and even more so durring the
technical revolution. Most of the borrowed words are from (
British)
English, but they have used words from a few other languages like
German (ex.
arubaito),
Portugese (ex.
tempura) and others (but I can't think of any more
examples right now).
The way they use katakana to make these words Japanese
compatable is by attempting to
recreate the
sound of the original word with the
phonetics of the Japanese language.