What Is Standing Meditation or Zhan Zhuang?

From Wikipedia: https://en.wikipedia.org/wiki/Zhan_zhuang

Zhàn zhuāng, literally: "standing like a post", is a training method often practiced by students of neijia(internal kung fu), such as YiquanXing Yi QuanBagua Zhang and Taiji QuanZhan Zhuang is sometimes translated Standing-on-stakeStanding QigongStanding Like a TreePost-standingPile-standing, or Pylon Standing. It is commonly called a form of Qigong, despite the differences from other Qigong methods in Zhan zhuang's orientation.[1]