Tell me about the United Nations

The united Nations exercice a worldwide responsability and, yet, too often is
little known by the general public. When and why was the United Nations
founded ? What are its ideals, its goals and the means at its disposal for
reaching them ? What is its structure ? How does it function ? What are the
problems it faces day-to-day and in the long term ?
How can the men and women who head the organization and work for it, set aside
the conflicts their own countries are involved in and devote their energies to
the realization of mankind's loftiest goals: the establishment of a just and
lasting peace for all in the world ?

*[XVIIIe]: 18e siècle
*[ xix e]: 19e siècle
*[3e]: Troisième