A present participle is a verb form that ends in "-ing" and is used to indicate ongoing action. It can function as part of a verb tense, such as in the present continuous tense, where it helps describe actions happening right now, like in the sentence "She is running." Additionally, the present participle can act as an adjective, providing more information about a noun. For example, in the phrase "the barking dog," the present participle "barking" describes the dog’s action. This versatility makes present participles useful in both writing and speaking.