Adverbial phrases are groups of words that function as adverbs to modify a verb, adjective, or another adverb in a sentence. They provide information about time, manner, place, reason, or degree. Common examples of adverbial phrases include "in the morning," "with great care," "on the table," "because of the rain," and "to a certain extent." Adverbial phrases can be placed at the beginning, middle, or end of a sentence.