Answer:
These are referred to as adverbs. Adverbs are words that modify a sentence, and often end with a prefix of ly-. For example, "I walk to the park slowly". That sentence has an adverb, slowly, which modifies the sentence so we know that the writer is slowly walking to the park. Now, without that adverb, we would not know that the writer is slowly walking to the park, we would just know they are walking to the park. That is how adverbs modify sentences.