Okay kiddo, so there was this guy named Zadok in the Bible who was a priest. His family, the Sons of Zadok, were very important priests in the Israelite religion. They were in charge of offering sacrifices in the temple and making sure everything was done correctly.
Later on, in the book of Ezekiel, God said that the Sons of Zadok would be the only ones allowed to perform certain rituals in the temple. This meant they were super important and respected by all the other priests and the people.
So basically, the Sons of Zadok were a special group of priests who had a very important job in the temple and were considered to be very important in their religion.