You’re probably now asking yourself what a gerund is. A gerund is a word that ends in “ing.” It is normally a verb, but it is now being used as a noun.
For example, I like writing. (Writing is a gerund.)
The trick with a gerund is that if a noun or pronoun precedes it, it must be in the possessive form.
I appreciate you helping me.?(Helping is a gerund. The pronoun in front must be possessive.)
I appreciate your helping me. (Your is a possessive pronoun.)
The plane landing on time surprised us.?(Landing is a gerund. The noun in front must be possessive.)
The plane’s landing on time surprised us.
Possessive pronouns are my, your, his, her, our, and its.