What is a fronted adverbial?
Adverbials are words or phrases that give more information to the sentence.
"I discovered fronted adverbials earlier today."
'Earlier today' is the adverbial.
A fronted adverbial is when the adverbial word or phrase is moved to the front of the sentence, before the verb.
"Earlier today, I discovered fronted adverbials."
So here, 'earlier today' is a fronted adverbial.