Writing Type / System

Japanese writing is formed by 3 types: Hiragana, Katakana, and Kanji.

Hiragana is used for particles (like "from", "to", "-san") or to support Kanji. All children up to when they start learning Kanji, all infants will use Hiragana.

Katakana is used for foreign word or name.

Kanji is Chinese character-driven but not actually same as chinese words today. There are about 50,000 words in kanji. Don't worry, most Japanese don't know ALL, but I'd say about 30,000 depends on the field that THAT person is into. We use combination of kanji to make words. For example, "社会(しゃかい・sha kai)" means "in society" or "in business world". However, if you reverse the characters to "会社（かいしゃ・kai sha）" it will mean "a company". Even if it sounds the same, you really need to focus on how it is used in character or by phrase. For example, "漢字（かんじ・kan ji）"　is "kanji (this japanese writing discussing now)", but "感じ（かんじ・kan ji）" means "feels like～".

Please take a look at blogs "Hiragana" and "Katakana" for simpler clarification.