Parallax is an effect where the background is moved at a different speed than the foreground content while scrolling.
to apply the parallax effect on a block element add class parallax-bg with attribute data-src for the background image url.
scroll down to see the effect and the code.
<div class="parallax-bg" data-src="images/bg.jpg"></div>
to make A video background create a container with class video-bg then put your HTML5 Video Code inside of it.
<div class="main-container">
<!-- Video BG -->
<div class="video-bg">
<video poster="images/poster.jpg" autoplay loop>
<source src="images/bg.mp4" type="video/mp4">
</video>
</div>
<!-- // Video BG -->
</div>