A gerund is a form of the verb that acts as a noun.
A gerund is a common part of speech and it is formed by adding "-ing" at the end of the word. Moreover, gerunds can work as nouns in a sentence. For example, in the sentence "Swimming is good for your health" the gerund "swimming" is functioning as a noun and the head word of the subject. However, gerunds must not be confused with present participles, which also end in -ing. Unlike gerunds, present participles act as verbs or adjectives.