First, the // means to start at the root and select all elements (that match the selectors and criteria that follow), regardless of where they are nested.
One strand: To make the single-strand noodle, the chef first prepares the dough by rolling out a thin log that is then laid flat in a spiral (it somewhat resembles a lollipop).
First, the Court required especially strict scrutiny of legislation that employed a "suspect classification", meaning discrimination against a group on grounds that could be construed as racial.
First comes the family, then an association of families in a tribe, then a further association in a village, and then you might say an association of villages that create a polis or a city.