A. Adverbs are formed from an Adjective + ly: quick/ serious/ careful/ quiet/ heavy/ bad
A1. Some adjectives end in ~ly: friendly/ lively/ elderly/ silly/ lovely

B. Adjectives tell us about a noun, use adjectives before nouns: Jon is a careful driver
B1. Adverbs tell us about a verb: Jon drove carefully along the narrow road.
B2. use adjectives after some verbs, especially be, and also look/ feel/ sound etc. (e.g. I feel happy, The children were playing happily)

C. use adverbs before adjectives and other adverbs. (e.g. reasonably cheap, incredibly quickly)
C1. use an adverb before a past participle (injured/ organised/ written etc.) seriously injured, badly organised.