Quoted from the Book of Wisdom by Chan Master Wu Jue Miao Tian.
The Chinese word Chan originates from the Sanskrit word dhyana, meaning quiet meditation. Most people think of Chan as sitting quietly or sitting meditation. This is however only the external form of Chan. The essence of Chan rests in cultivating the absolute wisdom in meditation and witnessing the absolute Truth with the absolute wisdom.
So, sitting meditation is less about sitting and more about meditation. Sitting meditation is not just sitting quietly, nor is it sitting for the sake of sitting. Sitting meditation is to meditate on the true nature of reality and witness the absolute wisdom. Through sitting meditation practice, the Truth is realized first-hand at the heart. This is very different from intellectual understanding.
Picture from: http://www.huffingtonpost.com/jeanne-ball/meditation-tips_b_3791316.html