What does Numbers 8:19 mean?

I have given the Levites as a gift to Aaron and his sons from among the Israelites, to do the work at the tent of meeting and to make things right for the Israelites, so there will be no disaster among them when they come near the sanctuary. Numbers 8:19 - Modern Text Bible

(The Levites serve as a protective buffer, doing the sacred work so the rest of the people are safe from the dangers of approaching God's presence unprepared.)