"Poetry without words" talks about the beauty of implication, emphasizing that the connotation and meaning expressed by calligraphy are as vivid, implicit, meaningful and intriguing as poetry, while "invisible dance" refers to the beauty of calligraphy's posture, the thickness, length, straightness, correctness, gravity and urgency of strokes, and the intensity, depth, dryness and plainness of pen and ink.
In a word, these two sentences are a high summary of the unique calligraphy art of the Han nationality, which I like.