So this last week before the fall semester starts, I decided to improve my knowledge of Japanese writing, some. Specifically, I wanted to learn all of the hiragana and katakana (I already knew all but 6 of the hiragana), as well as 100 kanji (although that last part got torpedoed by a particular circumstance). If you have no idea what those three words mean, let me explain the basics of how Japanese writing works.
Japanese is composed of a very simple sound set: about 14 consonants and 5 vowels (note that English doesn't really have 21 consonants and 5 vowels, as many letters can be pronounced in different ways - i.e. there are about a million vowel sounds in English). Syllables in Japanese are a fixed unit of time that the syllable is spoken, regardless of which syllable it is. Syllables can be composed of a vowel alone, a consonant followed by a vowel, or a consonant alone; however, only a couple of consonant can exist without a succeeding vowel (n and s come to mind). Because of this very simple structure, it was decided that the phonetic alphabet would consist of one character per syllable. All in all this comes out to 71 characters; of these, 25 are duplicates of other characters, but carry some simple decoration to distinguish them.
There are actually two phonetic alphabets consisting of these same characters - the hiragana and katakana. Each has a character for each syllable, but the symbols for each alphabet differ. Hiragana is used to write (most) Japanese words. Katakana is used for borrowed words (that have been incorporated into Japanese - English is notorious for borrowing words) and to spell out foreign words (and when the words can't be exactly represented in the Japanese syllable set, you get the characteristic Japanese accent).
If this were all there was to the Japanese writing system, it would not be extremely difficult to learn. The problem is that, in addition to these two phonetic alphabets, Japanese usually uses something different for verbs, nouns, and sometimes adjectives/adverbs: the dreaded kanji. Kanji are Chinese pictographs, of which there are around 50,000, and the primary reason that learning Japanese is less fun than a root canal. Each kanji represents one particular word or idea, and the average Japanese adult needs to know around 2000 of these pictographs in order to get by.
Despite the use of Chinese pictographs, Japanese is not actually related to Chinese. The same kanji will generally mean the same thing in both Japanese and Chinese, but the spoken word for the kanji will differ. The Japanese simply decided to use the Chinese pictographs, rather than inventing a writing system from scratch. From what I've heard, the hiragana and katakana were developed after the adoption of the Chinese writing system, by aristocratic women with a substantial amount of free time, yet little formal education in writing (and, obviously, it takes a LOT of education to learn the Chinese writing system).
So, that's a simplistic overview of the Japanese writing system. I left out a number of things that I know, and there are surely things I don't. But that should give you an idea how it works, and why it's so difficult to learn (although still not as hard as Chinese, due to the fact that ALL words in Chinese are represented by pictographs, and so there are more of them to learn).
As a final note, it's thought by some that Japanese and Korean are sister languages; even from my very limited knowledge of the two languages, I can see a moderate number of words that are similar. Korean, however, uses an elegant phonetic alphabet in which each symbol represents a single sound, sort of like English (if I recall correctly, there are 14 consonants and 14 vowels in Korean). Each square kanji-looking Korean character is actually a single syllable, which is a composite of multiple sound symbols arranged in an order I don't really understand. As well, Korean does not have the same consonant-vowel-syllable structure as Japanese, and may have more than three sounds per syllable (three referring to a consonant and a diphthong, which I didn't discuss in this post). Best of all, Korean does not use (or rather, rarely uses, as at one point it did use) those terrible Chinese pictographs.