extremely is an adverb of degree, which is used to indicate the level that an action is taking place. It is used to add emphasis and lend more weight to a phrase or sentence.
1. I was extremely wary of trusting her again.
2. She is extremely talented at singing.
3. They are extremely disappointed that their plans were cancelled.
Adverbs of degree are sometimes used with contrasting adverbs to create a more balanced sentence. For example, 'She is extremely talented but also very humble.' Additionally, it is important to remember that extremely is an absolute adverb, meaning it cannot be used with words such as 'a little bit' or 'slightly'.