An adverb modifies a verb, adjective, or another adverb. It answers questions like:
* How? (She sang beautifully.)
* When? (He arrived yesterday.)
* Where? (They walked down the street.)
* To what extent? (He was completely exhausted.)
* Why? (He went to bed early because he was tired.)
Therefore, "pang-abay" in Tagalog directly corresponds to "adverb" in English, which describes the manner, time, place, degree, or reason of an action or state.