What is meant by unit of society

"The family is the original cell of social life. It is the natural society in which husband and wife are called to give themselves in love and in the gift of life. Authority, stability, and a life of relationships within the family constitute the foundations for freedom, security, and fraternity within society. The family is the community in which, from childhood, one can learn moral values, begin to honor God, and make good use of freedom. Family life is an initiation into life in society."