Check out example codes for "adjecent sibling selectors". It will help you in understanding the concepts better.

Code Example 1

/*The adjacent sibling combinator (+) separates two 
selectors and matches the second element only if 
it immediately follows the first element, and
both are children of the same parent element.*/

li:first-of-type + li {
  color: red;
}

<ul>
  <li>One</li> // The sibling 
  <li>Two</li> // This adjacent sibling will be red
  <li>Three</li>
</ul>

Code Example 2

/*Adjacent Sibling Selector
The adjacent sibling selector (+) selects all elements 
that are the adjacent siblings of a specified element.
Sibling elements must have the same parent element,
and "adjacent" means "immediately following".
The following example selects 
all <p> elements that are placed immediately after <div> elements:*/

div + p {
  background-color: yellow;
}

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