Check out example codes for "how to make parallax scrolling website using bootstrap". It will help you in understanding the concepts better.

Code Example 1

.parallax { 
  /* The image used */
  background-image: url("img_parallax.jpg");

    /* Set 
a specific height */
  height: 500px; 

  /* Create the parallax scrolling effect */

background-attachment: fixed;
  background-repeat: no-repeat;
  background-size: cover;

<!-- Container element 
<div class="parallax"></div>

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