A Permanent Representative (sometimes called a "UN ambassador") is the head of a diplomatic mission to the United Nations Organization (or United Nations, UN). Of these, the most high-profile UN Permanent Representatives are those assigned to headquarters in New York City (U.S.). However, member states also appoint Permanent Representatives to the other UN offices in Geneva (Switzerland), Vienna (Austria), and Nairobi (Kenya).
Many countries, including the United States, call their UN Permanent Representatives "U.N. ambassadors". Although a Permanent Representative holds the equivalent diplomatic rank of an ambassador (or Chief of Mission or High Commissioner), he or she is accredited to an international organisation, and not to a Head of State (as a nation's ambassador would be) or to a Head of Government (as a High Commissioner would be).
Representatives to UN councils 
Some diplomats are representatives to UN councils, such as the Economic and Social Council of the United Nations.
Goodwill Ambassadors 
UNESCO has Permanent Delegates heading the diplomatic missions to the organisation, rather than Permanent Representatives. However, there are also UNESCO Goodwill Ambassadors, such as many American celebrities who act as a UNESCO Goodwill Ambassador to a particular nation. UNHCR has similar UNHCR Goodwill Ambassadors.
A UN Permanent Representative is sometimes called an Ambassador to the UN, or rarely, a UN Permanent Ambassador, to distinguish the position from being a UNESCO Goodwill Ambassador. However, again, the term "ambassador" is more commonly used to describe each of nation's government officials who are assigned to handle some affairs with another nation.
See also