Preposition states the position of a particular noun or a pronoun in a sentence. It usually helps us understand the relation between the words. That is without preposition it becomes difficult to determine the position of the Noun. For example, Sindhu prepared the batter for the cake and put it in the oven for it to bake. Here, without the word IN, it would not be possible to know where Sindhu was putting the batter to bake. Hence, IN becomes the preposition.