The second alphabet, katakana, is just a different set of characters, representing the same syllables as hiragana, making the same noises. So why have it? Well, it's mainly used for words of foreign origin which have found their way into the Japanese language. Just as English has cafe, ennui and savoir-faire, Japanese has sentaa (centre), miruku (milk) and ruususokkusu (loose socks).

These so-called "loan words" are written using katakana syllables, not hiragana. This may sound like an unnecessary complication, but in fact it can be quite helpful. If confronted with a sheet of indecipherable Japanese, containing mainly kanji and hiragana, the katakana (if there is any) stands out because of the simplicity of its strokes. With a little practice, your eye is easily drawn to it and you can be pretty sure that it will be spelling a word you're going to recognize, such as "intaanetto" (internet), "nyuusu" (news), "orenjijuusu" (orange juice) or "supagettimiitosoosu" (spaghetti with meat sauce). It's worth learning for Italian restaurant menu reading alone.

It's really not that odd if you think about it; after all, there is a very close parallel with English: our use of uppercase and lowercase letters. There are at least two ways of writing each of our 26 letters, and which you should use depends on the context. So relax - you've already been using two alphabets your whole life without realizing it.

Katakana is also used for emphasis (especially on TV subtitles), foreign names and rude words. You may draw whatever conclusions you wish from that.