Gerunds are verb forms ending in "-ing" that can function as nouns. They can act as subjects, objects of verbs, or objects of prepositions. As subjects, gerunds refer to actions. As objects of verbs, gerunds indicate the action that follows certain verbs like enjoy, dislike, and prefer. As objects of prepositions, gerunds describe actions related to other nouns in the sentence. In all cases, gerunds allow verbs to take on nominal roles within sentences.