Parent elements and resizing?

First off, what even is a parent element? tried looking it up online, and I’m not understanding.
I’m tryibng to build a survey page and keep getting an error message. Below are my code and the error message.

img {
max-width: 100%;
  display: block;
  height: auto;
  margin: 0 auto;
}
  1. The element should responsively resize, relative to the width of its parent element, without exceeding its original size.
    Try using the “max-width” style property : expected ‘none’ to not equal ‘none’
    AssertionError: Try using the “max-width” style property : expected ‘none’ to not equal ‘none’

Can you post a link to your project (i.e. Codepen)? We need to see your full code to be able to help you further.

the parent element is the one with the child element nested inside it
parent/child is a way to talk about nested elements. the child is nested inside the parent

<header>
    <h1> This is the text </h1>
</header>

– In this block of code, header is the parent element of < h1> element and <h1> element is child of header element.
I hope this will give you a clear idea. If still confusion please feel free to write in comments.