In Numbers, God has given the Levites to Aaron, the high priest, and his son. The Levites are separated by their families and each are given a specific task in helping to set up the tabernacle as it moves from place to place.
God assigned the Levites a specific task because He knew that in the wilderness that they were traveling through, they would be faced with different cultures, and several enemies. If there was chaos, and disorganization, the enemy would surely defeat them. Much as each Levite family had a task, each member of a church family has a specific gift or task that God has blessed them with. It is our responsibility and duty to God to do that specific task, whatever it may be. If we follow as the Lord has instructed, He will bless us for doing our part.