Katakana

Katakana is a form of Japanese writing which is transcription of foreign word or foreign name that is not Japanese or some early Chinese driven.

Again, katakana is made from chinese letters like hiragana. (please take a look at hiragana blog if interested.)

For example, Japanese had rice from the earlier stage. Thus we will have the word, "kome" (rice). In hiragana would be こめ, or in Kanji 米 (this form is used unless you're an infant). However, foreign word like computer, you will use katakana konpyu-ta- (how it is written in Roman alphabet that Japanese use) コンピューター. Yeah, it is hard to know that konpyu-ta- is computer. But if you really seek how it pronounces, you'll get it eventually.

Below would be the chart of katakana.