所謂三大部門,即是以「政府」為主的「第一部門」、以「企業」為主的「第二部門」、以及以「非營利組織」 (Non-Profit Organization, NPO) 或「非政府組織」(Non-Government Organization, NGO) 為主的「第三部門」。第一部門的運作媒介主要為「權力」,第二部門的運作媒介主要為「貨幣」,第三部門的運作媒介則主要為「溝通及說服」。「權力」具有普遍性的強制力量,「貨幣」滿足人類的物質需求,至於「溝通及說服」則合乎人類的理想追求。就產出與社會功能而言,第一部門的產出主要為「秩序」與「公共財」,第二部門的產出主要是「財貨及勞務」,第三部門的產出則主要為「服務」及「精神價值」。由於企業部門主要功能是在物質層次上發展的,而政府部門的功能主要為道德層次(倫理規範)以及物質層次(公共財),兩者皆無法滿足人類其他生命層次的追求,因此非營利組織遂有蓬勃發展的現象。隨著人類物質條件以及經濟活動的改善,人類不再只是關心低層次的安全與生存問題而已,而是進一步地追求情感、道德、精神的實踐與滿足。非營利組織於是勃然而興,且扮演愈來愈重要的角色。由於非營利組織的理想性格遠遠高出政府部門以及企業部門,因而愈來愈受到人們的尊敬與讚佩,從而也將發揮愈來愈強大的影響力。
The so-called three branches include the "first sector" (government), the "second sector" (enterprise) and the "third sector" (non-profit organizations or non-government organizations). The operation of the "first sector" depends on "power," the operation of the "second sector" depends on "money," and the operation of the "third sector" depends on "communication and persuasion." The outputs of the "first sector" are "social order" and "public goods," the outputs of the "second sector" are "goods and services", and the outputs of the "third sector" are "ideal and spiritual values." The "first sector" meet the public and security needs of the people. The "second sector" meet the material needs of the people. Both are unable to meet the needs of the human spirit and morality. Therefore, non-profit organizations came into being. With the development of the human material conditions and economic activity, people began to pursue emotional, moral, and spiritual needs. Thus, non-profit organizations rise and play an increasingly important role.