Adverbs are, of course adverbials, but not all adverbials are adverbs.
Match the term in italics to the definition.
He left by bus.
He left last August.
He left when he saw me.
He left because he need to catch a train.
He left through that door.
He left at six o'clock.
He left sobbing loudly.
He left earlier.
He left slowly.
He left to get his train.
adverb - manner
adverbial - time clause
adverbial prepositional place phrase
adverbial - prepositional time phrase
adverbial - non-finite (participial) clause
adverb - time
adverbial clause - reason
adverbial - infinitive of purpose
adverbial - noun time phrase
adverbial - prepositional manner phrase