It refers to a word or phrase that modifies a verb, adjective, or another adverb, typically expressing manner, time, place, or degree.
For example:
* Pang abay: mabilis (quickly)
* English: quickly
* Pang abay: sa bahay (at home)
* English: at home
* Pang abay: napaka-masaya (very happy)
* English: very happy