how the style rule is applied to only unordered listed contained as immediate children of navigation elements. code example

Example 1: css apply style to direct children

/*
Use the ">" selector to apply css to direct children of a parent element.
example: https://jsfiddle.net/dbeachnau/54w6x0pj/2/
*/

.parent > .child { color:red; }

Example 2: how to use child selectors in css

ul li { margin: 0 0 5px 0; }
ul > li { margin: 0 0 5px 0; }