A gerund is a verb form that ends in "-ing" and functions as a noun.
Here are some examples:
* Swimming is my favorite exercise. (The gerund "swimming" is the subject of the sentence)
* I enjoy reading. (The gerund "reading" is the object of the verb "enjoy")
* He's good at cooking. (The gerund "cooking" is part of a prepositional phrase modifying "good")
Let me know if you have any other questions!