A. Adjective: We use adjectives to describe nouns. Most adjectives can be used in front of a noun or after a link verb: be, look or feel.
B. Adverb: A word or phrase that modifies the meaning of an adjective, verb, or other adverb, expressing manner, place, time, or degree. Some adverbs like sentence adverbs, can also be used to modify whole sentences.
C. Adverbial: A word or phrase functioning as a major clause constituent and the adverbial is an adverb, adverbial phrase or adverbial clause which gives us additional information about the time, place, or manner of the action which is described in the rest of the sentence.