A clause from sentence 1 has been turned into a ______ in sentence 2?

Question

1.Since she knew what the lecture was about, she didn't attend the meeting.

2.Knowing what the lecture was about, she didn't attend the meeting.

My aswer is Relative Pronoun is that correct?
Thank You

"Knowing what the lecture was about" is called a participial phrase in the sentence 2 example, since it functions as a modifier of "she". "Knowing" is a (present) participle. Although "-ing" words are called gerunds, "Knowing what the lecture was about" is not a gerund phrase, because such phrases are used as nouns.

reference:
http://www.ucalgary.ca/UofC/eduweb/grammar/course/sentence/2_4d.htm