This is a way of presenting video content, which can play videos on a large screen and occupy a small area, which was previously only unique to iPad.
The usage is very simple. Just look for the "Picture in Picture" button, and you can open the "Picture in Picture" playback in domestic apps such as Aifaner, Bilibili, Youku, etc.
// video
After opening "Picture in Picture", the small video window can be dragged to any position, or directly hidden in the sidebar, without interrupting the audio.