The United Nations, its programmes and funds, and the specialized agencies comprise the "UN system". The UN as such, is made up of six main organ with specific tasks and functions :

• General Assembly
• Security Council
• Economic and Social Council
• Trusteeship Council
• International Court of Justice
• Secretariat

With the exception of the International Court of Justice in the Hague, the Netherlands, all principal organs are based in New York. 

The Charter is the constituting instrument of the United Nations, setting out the rights and obligations of Member States, and establishing the Organizations main organs and procedures. 

The United Nations family, however, is much larger. In the system of the United Nations, a number of functional institutions concerned with the accomplishment of specific tasks are integrated , encompassing 17 agencies and several programmes and bodies, each with its own structure, membership, governing bodies and budgets. Together, they provide technical assistance and other forms of practical help in virtually all areas of economic and social endeavour.  

The logic of the UN documentation system is the logic that is necessary for the representatives of states in the United Nations to work within the processes and procedures of the Organization. Therefore, retrieving UN documents and reports requires a comprehensive knowledge of the basic structure and processes of the United Nations Organization. All documents reflect this structure, being issued by the UN entity where a certain question has been dealt with.  

UN documents are issued by the core Organization, whereas the specialized agencies have there own publishing and depository library system.