will作为助动词时与句子谓语构成将来时态;
作为情态动词时表示“愿意”“意愿”
1. 表示请求、建议等,would比will委婉客气。如: Would you pass me the book? 2. 表示意志、愿望和决心。如: I will never do that again. They asked if we would do that again. The door won't open 3. 用“will be”和“will(would) + have + 过去分词”的结构表示推测,主要用于第二、三人称。前者表示对目前情况的推测,后者表示对已经完成的动作或事态的推测。如: This will be the book you want. He will have arrived by now. The guests would have arrived by that time. I thought you would have finished this by now. 4.will表示习惯、请求,固有性质等。 Everyday he will sit here hour after hour doing nothing.(习惯) Will you help me with my English?(请求) 5.Would可表示过去反复发生的动作或某种倾向。Would表过去习惯时比used to正式,并没有“现已无此习惯”的含义。如: The wound would not heal. During the vacation he would visit me every week. 。6. 表料想或猜想。如: It would be about ten when he left home. What would she be doing there? I thought he would have told you all about it.
参考资料:http://baike.baidu.com/view/190314.htm#5_6