Here's why:
* Prepositions (words like "on", "in", "to", "with", "at", etc.) always require an object.
* This object is usually a noun or a pronoun, which clarifies what the preposition is referring to.
Examples:
* On the table (table = noun)
* In the house (house = noun)
* To him (him = pronoun)
* With her (her = pronoun)
Let me know if you have any other questions!