Kanji is one of letters used in Japanese. Kanjis are ideograms. It means a kanji has meaning (s) like a word. e,g.
山 yama (mountain)
川 kawa (river)
Kanji were important from old Chinese countries Kan and Go. So, they are called kanji that means “Kan letters “. However, Japanese cannot write with only kanji , so phonograms, hiragana and katakana were made from kanji that have the same pronunciations.