Video HTML5
Before HTML5, a video could only be played in a browser with a plug-in (like flash).
Now you can use HTML5 video tags.
So it is not necesarry anymore to have Javascript or Flash players anymore.
Only upload your video and add an HTML element in your question.
With the following code:
<html>
<video height="280" width="500" controls autoplay>
<source src=".mp4" type="video/mp4">
Your browser does not support HTML5 video.
</video>
<br /><br />
</html>
In the video tag you can decide to use controls (so people can click on play/resume) and autoplay (so the video is automatically playing when the page is loaded).
More information in general about the video tag:
https://www.w3schools.com/html/html5_video.asp