一个是动词一个是名词，动词可以做谓语或者主语，而名词只能做宾语。i want to do sth表示我想要做某事，后接宾语。i want to do sth表示我想要做某事，后面不能直接动词，而是接名词或者形容词，或者是
动名词，如果是接名词的话，要用动名词的现在进行式，而不能用
一般过去时。例如：I want to go swiming tomorow morning.I want to buy a bok yesterday.I want to go to Beijing tomorow.I want to buy a new bike.我想明天去游泳。我想买一本书昨天我想去北京。我想买一辆新自行车。i want to do sth表示我想要做某事，后接
动词不定式，或者动名词，如果是接动名词的话，要用动名词的现在进行式，而不能用一般过去时。I want to buy some aples.I want to buy a new car.