The ancestors of Chinese people initially built characters by the method of resembling the shape and configuration (pictographs), which means that the writers draw the shapes or configurations of objects with lines so as to form words. For example, "日"(sun) looks like the sun, "月"(moon) looks like the moon, "山" (hill) looks like a hill, "水"(water) looks like a river and "目"(eye) looks like an eye.
But there is a great limitation of forming words by drawing pictures, and some objects and affairs cannot be described by drawings, thus some new means of word-forming such as self-explanatory characters, associative compounds and pictophonetic characters were invented.
Self-explanatory characters mean expressing meaning by simple symbols, for example, in the characters "上"(up) and "下"(down), a long symbol and a short symbol are used to express the upper side part and underside part of a plane; in "本"(root) and "末"(treetop), a short string underneath and a short string upside are respectively used to indicate the positions of a root and treetop; the point in a knife edge (刀口) indicates blade (刃).
Self-explanatory characters mean that combining two or more characters together to form a new character with new meaning. For example, "休"(rest) means that a person is leaning against a tree to relax himself, "家"(home) means that there is a pig in a house, and "明"(bright) is composed of "日"(sun)and "月"(moon), which expresses brightness.
Pictophonetic characters are made up by two parts, namely the semantic element and phonetic element, and the former one indicates the meaning while the later one indicates the pronunciation. 90% of Chinese characters are pictophonetic characters. For example, in the character "材" (timber), the left "木" is the semantic element and the right "才" is the phonetic element; in "贷", the upper "代" is the phonetic element and the lower "衣" is the semantic element.