The Alphabets
Japanese consists of two alphabets (or kana) called hiragana and katakana, which are two versions of the same set of sounds in the language. Hiragana and katakana consist of a little less than 50 "letters", which are actually simplified Chinese characters adopted to form a phonetic alphabet.
Chinese characters, called kanji in Japanese, are also heavily used in the Japanese writing. Most of the words in the Japanese written language are written in kanji (nouns, verbs, adjectives). There exists over 40,000 kanji where about 2,000 represent over 95% of characters actually used in written text. There are no spaces in Japanese so kanji is necessary in distinguishing between separate words within a sentence. Kanji is also useful for discriminating between homophones, which occurs quite often given the limited number of distinct sounds in Japanese.