Complex sentence: She explains the human concept of knighthood and that Connie will serve as Steven's knight, and then re-summons Holo-Pearl (the holographic version of herself introduced in "Steven the Sword Fighter"), who acts as a sparing partner for Connie's training.
Split into simpler sentences: She explains the human concept of knighthood and that Connie will serve as Steven's knight. Pearl then re-summons Holo-Pearl (the holographic version of herself introduced in "Steven the Sword Fighter"), who acts as a sparing partner for Connie's training.