Describes (modifies) a verb, adjective, or another adverb; quickly silently, well, badly, very, really.
Ex: My patience wears **quickly** (Quickly modifies Wears \[V.\])
When I am **very** bored, I tire **really** **easily** (Very modifies bored \[Adj.\], Really modifies easily \[Adv.\], Easily modifies tire \[V.\])