Adverbs of Manner add more information to verbs to make them more specific. For example “He ran” doesn’t say much about how he ran. If you add an adverb it will solve this problem: “He ran quickly” gives us more information and sounds better.
Adverbs of Manner always come after a verb and can be used with words like very or too. Adverbs of Manner are adjectives that almost always end with –ly, though some are also irregular.
Lesson by Seb, teacher at EC Cape Town English school
Link: How to use adjectives and adverbs