My cat's favorite food is salmon. The police arrested him for criminal activity. Gerunds and gerund phrases virtually never require punctuation. The term verbal indicates that a participle, like the other two kinds of verbals, is based on a verb and therefore expresses action or a state of being. However, since they function as adjectives, participles modify nouns or pronouns.
Present participles end in -ing.
In order to prevent confusion, a participial phrase must be placed as close to the noun it modifies as possible, and the noun must be clearly stated. If the participle or participial phrase comes in the middle of a sentence, it should be set off with commas only if the information is not essential to the meaning of the sentence. Note that if the participial phrase is essential to the meaning of the sentence, no commas should be used. If a participial phrase comes at the end of a sentence, a comma usually precedes the phrase if it modifies an earlier word in the sentence but not if the phrase directly follows the word it modifies. Participles and participial phrases must be placed as close to the nouns or pronouns they modify as possible, and those nouns or pronouns must be clearly stated.