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. Selectors that utilise a descendant combinator are called descendant selectors.
body article p {
color: red;
}Source: https://developer.mozilla.org/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators