Quickly, what's an adverb?

Indian teacher aims to be listed in Guinness as world's fastest grammarian.

He says he can teach

tense in 30 seconds; change the voice in 50 seconds; indirect speech in one minute and 20 seconds; punctuation in one minute and 10 seconds; clauses in one minutes and 25 seconds; simple, complex and compound sentences in one minute 55 seconds; figures of speech in three minutes.

The only question left to be answered: Why?