1. What is a preposition?
　　A preposition is used before its object, a noun, a pronoun or a phrase, to form a phrase to show place, position, direction, method, time, object, aim, the passive, etc., as in English, e.g.
 
从(from) 　　 自从(since) 　　 当(when) 　　 在(at) 　　 到(to) 　　 向(towards) 　　
朝(towards) 　　 与(with) 　　 用(with) 　　 以(by) 　　 让(let) 　　 比(than) 　　 
把(hold) 　　 被(by) 　　 为(for) 　　 为了(in order to) 　　 对于(for) 　　 
关于(about) 　　 通过(through) 　　 根据(according to) 　　 依照(following) 
 
 
2. What is noteworthy about Chinese preposition 
 
2.1. A preposition never goes alone
 
　　A preposition cannot be an element of a sentence by itself. It is only used with its object to form a phrase modifying another word or phrase. So, you can easily differentiate between a preposition and a non-preposition, e.g. (The prepositional phrases are highlighted in red)　
 
　　他在北京。(He is in Beijing.) ---- The "在" is a verb used as the predicate of the sentence.
　　他在北京工作。(He works in Beijing.) ---- The "在" is a preposition used with "北京" to form the phrase "在北京" modifying the verb "工作".
　　大门朝南。(The gate faces south.) ---- The "朝" is a verb used as the predicate of the sentence..
　　大门朝南开。(The gate opens towards the south.) ---- The "朝" is a preposition used with "南" to form the phrase "朝南" modifying the verb "开". 
 
2.2. The preposition "被" can be used with a "zero object" to form a phrase
 
　　The preposition "被" can be used with a "zero object" (that is to say, no object) to form a prepositional phrase modifying another word or phrase, e.g.
 
used with its object used with a "zero object"
他被警察逮捕了。
(He was arrested by the policeman.) 他被捕了。
(He was arrested.)
树被他的哥哥砍倒了。
(The tree was cut down by his brother.) 树被砍倒了。
(The tree was cut down.) 
 
 
2.3. The economical use of the preposition in Chinese
 
　　The number of prepositions in Chinese is much fewer than that in English. In many cases, people do not use any preposition, but let the meaning go without saying, e.g.
 
他左手写字。
 i.e. 他用左手写字。 (He writes with his left hand.)
她北京有家。 i.e. 她在北京有家。 (She has her family in Beijing.)
我们吃食堂。 i.e. 我们在食堂吃饭。 (We dine in hall.)
小偷逮着了。 i.e. 小偷被逮着了。 (The thief was caught there.)
这部小说译自中文。 i.e. 这部小说被译自中文。 (This novel is translated from Chinese.)