Selector and child selector, written as selector child-selector (div > p)

The child selector matches only elements that are first generation from the parent selector.

Text within a p directly below a div has a blue background

A title with an arrowhead that can be clicked on for additional details

In this case, the text does not have a blue background even though it is within a p that is within a div since p is not directly below div. Being within details and summary means that p is not a child but but perhas a child of a child or further down the line.

Text not within a div does not have a blue background.

Style

div > p {
  background-color: Lightblue;
}