* Prepositions show relationships: Prepositions like "on," "in," "to," "with," "about," etc., describe the relationship between a noun or pronoun (the object of the preposition) and another word in the sentence.
* Verbs express action or state: Verbs describe what the subject of the sentence does or is.
Example:
* Incorrect: "I am looking forward to go to the beach."
* Correct: "I am looking forward to going to the beach."
In the correct sentence, "going" is a gerund (a verb form acting as a noun) and serves as the object of the preposition "to."
In summary, the object of a preposition must be a noun, pronoun, or noun phrase, not a verb.