Many of us learned that it is incorrect to end a sentence with a preposition. Prepositions generally establish a relationship between other words or clauses, such as a relationship in time or position, an explanation of how something is done, the reason behind something, or possession (above, after, beneath, beside, during, for, with, up, etc.).
In reality, it is fine to end a sentence with a preposition, as long as the preposition is necessary to the meaning of the sentence. For example, in the sentence, “What are you thinking of?,” the preposition “of” is not necessary because it does not add meaning to the sentence. It would have been fine to ask, “What are you thinking?” However, if moving the sentence around to avoid ending it in a preposition becomes too formal sounding, stick with the preposition at the end. For example, “What is the movie about?” is preferred over “About what is the movie?” With the example, “The game was rained out.,” it would be impossible to move “out” to another position in the sentence.