Check out example codes for "descendent selector in css". It will help you in understanding the concepts better.

Code Example 1

The descendant combinator — typically represented by a single space ( ) 
character — combines two selectors such that elements matched by the second
selector are selected if they have an ancestor 
(parent, parent's parent, parent's parent's parent, etc) 
element matching the first selector. 

  h1 ul {
    border : 1px solid #f1f1f1;
Explanation: This above CSS code snippet will select all the 'ul' (unordered list)
			 tags which are preceeded by an 'h1' (header tag).
/*the best way to understand is to practice by implemetation.
Create a html file with lots of h1 and ul elements to understand by
implementing CSS on them*/

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