Japanese has 3 sets of writing, which I've mentioned before so it's very easy to differentiate between Chinese and Japanese. Historically, Japanese people have adopted Chinese characters, which is now called kanji (漢字, kana: かんじ) in Japanese. In Chinese language, Chinese characters are called hanzi (simplified: 汉字; traditional: 漢字) which is the only character that you'll see in a sentence.
There are 2 types of kana. Hiragana (kanji: 平仮名; kana: ひらがな) was invented by Murasaki Shikibu, the author of The Tale of Genji and it was used for women only. Katakana (kanji: 片仮名; kana: カタカナ), on the other hand, was used for monks only. Today, Japanese people use those 3 sets (hiragana, katakana, and kanji) to form a sentence. Hiragana today is used for native Japanese words. Katakana today is used for foreign words (a word that is not Japanese), onomatopoeia, etc. Kanji is used to express a word in a sentence, depending on the context.
Examples
Hiragana: car (くるま kuruma)
Katakana: computer (コンピューター konpyuutaa)
I hope this answers your question.
Edited by Tokura Misaki, 12 August 2015 - 11:38 AM.