What is the “-ing” form of a verb?

The “-ing” form of a verb is called the present participle. Present participles can be used as adjectives (e.g., “a thrilling story”) and to form the continuous verb tenses (e.g., the present continuous: “We are partying”).

Gerunds also use the “-ing” form of a verb, but they function only as nouns (e.g., “I don’t enjoy studying”).