Answer:
In the sentence above, "discovering" is used as a gerund.
Step-by-step explanation:
Gerunds are words that are formed with verbs but act as nouns. Therefore, they can be subjects, subject complements, or objects in the sentence. In this case, the gerund "discovering" functions as the object of the preposition "about". Verbs after prepositions take the -ing form. As this word is derived from a transitive verb, it selects an NP object ( a new hobby).