Adverbs that ask questions related to time, place, manner, frequency, reason, etc., are called Interrogative Adverbs.
- When did the mishap occur?
- How fast can this horse run?
- Where is the Machu Pichu located?
- How often does he visit you?
- Why did you do this?
- How good in studies is the new girl in the class?
The highlighted words when, how, where, how often, why and how in the above examples ask questions pertaining to the verb/adjective/adverb in their respective sentences.