What does Numbers 3:4 mean?

But Nadab and Abihu died in front of the Lord when they offered unauthorized fire in the desert. They had no children, so only Eleazar and Ithamar served as priests with their father Aaron. Numbers 3:4 - Modern Text Bible

(Nadab and Abihu died because they didn’t follow God’s instructions during worship. Since they left no children, only Eleazar and Ithamar continued as priests.)