Contextual Selectors

selector1 selector2 { ...rules... }

Often you'll see this as ways to apply different rules in header, main, and footer

main p {
/* rules for p inside of main */
}
footer p {
/* rules for p inside of main */
}
h2 {
/* rules for h2 everywhere*/
}
section h2 {
/* rules for h2 inside of section */
}
nav a:link,
nav a:visited,
nav a:hover,
nav a:active {
  /* rules for nav links */
}
footer a:link,
footer a:visited,
footer a:hover,
footer a:active {
  /* rules for nav links */
}