You can read the chapter (Society as a Human Product) in that book from which these ideas come...HERE. The most concise and relevant paragraph from this chapter is:
It is important to keep in mind that the objectivity of the institutional world, however massive it may appear to the individual, is a humanly produced, constructed objectivity. The process by which the externalized products of human activity attain the character of objectivity is objectivation. The institutional world is objectivated human activity, and so is every single institution. In other words despite the objectivity that marks the social world in human experience, it does not thereby acquire an ontological status apart from the human activity that produced it. The paradox that man is capable of producing a world that he then experiences as something other than a human product will concern us later on. At the moment, it is important to emphasize that the relationship between man, the producer, and the social world, his product, is and remains a dialectical one. That is, man (not of course, in isolation but in his collectivities) and his social world interact with each other. The product acts back upon the producer. Externalization and objectivation are moments in a continuing dialectical process, which is internalization (by which the objectivated social world is retrojected into consciousness in the course of socialization), will occupy us in considerable detail later on. It is already possible, however, to see the fundamental relationship of these three dialectical moments in social reality. Each of them corresponds to an essential characterization of the social world. Society is a human product. Society is an objective reality. Man is a social product. It may also already be evident that an analysis of the social world that leaves out any one of these three moments will be distortive. One may further add that only with the transmission of the social world to a new generation (that is, internalization as effectuated in socialization) does the fundamental social dialectic appear in its totality. To repeat, only with the appearance of a new generation can one properly speak of a social world. From Peter L. Berger and Thomas Luckmann. The Social Construction of Reality: A Treatise its the Sociology of Knowledge (Garden City, New York: Anchor Books, 1966), pp. 51-55, 59-61.