Chrome version 70 is required in order for this feature to work. You can get the full details by clicking on the source link below.
Whether the feature works depends entirely on whether the owner of a site has enabled it, so you won’t be able to use PiP with every video you encounter. It does work on YouTube, however, and this is a great place to test it out. Find a video and start it playing. Right click on the video window and the YouTube menu will appear. Right click again and the Chrome context menu will appear. Select the Picture in Picture option and you’re good to go.