They tend to use kanji (which are just Chinese characters) for most nouns and common verbs. Hirigana is used for their particles, tense conversions, and extensions to the kanji. katakana is used mostly for foreign words imported into the language and also for sound effects in manga.
Mostly, Japan uses pictographs, just like the Chinese do.
Korea abandoned pictographs in favor of a syllabic alphabet, but with more composite sounds than the alphabet used in the West.
In China, pictographs are used exclusively, since their particles are less important.
If you learn about 100 of them or so, you can read quite a bit of material from these countries, but in Japan, you must also learn the hirigana. Katakana is useful, since words imported into Japanese from English words are written in katakana. The Japanese often mispronounce these imported words in much the same way we mispronounce their words that we imported into English.