Adverbs are words that modify verbs, adjectives, or other adverbs. They tell us how, when, where, or to what extent something is done.
For example:
* quickly (modifies the verb "run")
* happily (modifies the adjective "happy")
* extremely (modifies the adverb "fast")
However, it's important to note that not all words ending in "-ly" are adverbs. Some words ending in "-ly" are adjectives, such as:
* friendly
* lovely
* lonely
Therefore, it's always important to consider the context of the word to determine its grammatical function.