Kanji are the characters from China, and they are very important for writing of Japanese language.
It is told that they were born in old China as many symbolic pictures
6,000 years ago and are formed like character 3,500 years ago.
Japanese people imported them from China around the 5th century and began to use for writing Japanese language.
And for matching characteristics of Japanese language, hiragana and katakana were created from kanji.
There are enormous numbers of kanji characters.
An authoritative kanji dictionary made in China in the 18th century has about 49 thousand characters.
Now in Japan, 2,136 characters for everyday use are specified.
We learn about 1,000 characters for 6 years in elementary school and other 1,000 characters for 3 years in junior high school.
Of course, other characters which is used in the name of people or places and old books are sometimes used, so Japan Industrial Standards defines the 6,355 kanji codes for computer.
Each kanji character has a meanings.
And the combination of two or more kanji character creates various meanings.
In China, most kanji character are read with one way, but in Japan one
kanji character has mostly multiple readings.
Because it has both reading of Chinese pronunciation when it was imported, and Japanese pronunciation assigened to the Japanese word.
Therefore, many Chinese or Korean say "Japanese language is difficult" though they also use kanji characters.
I show a part of the most basic kanji characters in the following.
These characters are mostly learned until the first or second grade of elementary school.