In English an adverb is a part of speech. It is any word that modifies any other part of language: verbs, adjectives (including numbers), clauses, sentences and other adverbs, except for nouns; modifiers of nouns are primarily determiners and adjectives.
Adverbs typically answer questions such as how?" (or "in what way?), when?, where?, why? and to what extent?. In English, they often end in -ly. When they answer how it is usually in what way. When they answer when it is usually a date or a word such as yesterday or today. When they answer why it is usually an explanation of a problem, issue, or situatiuon usually ending after because. When they answer where it usually states a place.
This function is called the adverbial function, and is realized not just by single words (i.e., adverbs) but by adverbial phrases and adverbial clauses.
An adverb as an adverbial may be a sentence element in its own right. Example: