"then they shall die": by the unqualified death penalty of the Torah — strangulation.
"also both of them": and not one who performs acts of arousal (without intercourse).
"also both of them": to include those who (might) cohabit with her after them.
"the man who lay with the woman" — though she be a minor;
"and the woman": even though she cohabited with a minor.
"and you shall remove the evil": Remove the doers of evil from Israel.
(Devarim 22:23) "If there be a na'arah, a virgin, betrothed": We are hereby taught that he is not liable (to stoning) unless she be a na'arah (and not a bogereth [viz. #238]), a virgin, and betrothed to a man (and not married).