I got myself confused about this the other day, went around searching for an answer and came up empty on finding something clear. The answer actually is quite clear and I feel a little silly for not knowing it.
With it in place, like this:
<video src="..." controls playsinline</video
Mobile browsers, will play the video right where it is instead of the default, which is to open it up fullscreen while it plays.… Read article “What Does `playsinline` Mean in Web Video?”