at表示目标，to表示方向。例如：He threw the book to me. 他把书扔给了我。He threw the book at me. 他用书砸我。He shouted to me. 他大声对我说。 He shouted 因此smile at sb意为对某人微笑。smile to sb. 朝着某人的方向微笑。二者的意思有差别，不能替换。

into是个动态介词，强调从外面到里面，常和动态动词连用。如He put the book into the box. 但不能说The book is into the box. in可以是介词也可以是副词。作为介词，既可以表示动态意义，也可以表示静态意义，以静态意义为多。如He put the book in the box. The book is in the box. He walked into the room. He is in the room. He is in.

onto和on的区别，类似于into和in的区别。不过on是在表面（接触），onto是到表面。He put the book on/onto the desk. The book is on the desk.