A diplomatic mission is a group of people from one state or an international inter-governmental organisation (such as the United Nations) present in another state to represent the sending state/organisation officially in the receiving state. In practice, a diplomatic mission usually denotes the resident mission, namely the office of a country's diplomatic representatives in the capital city of another country. As well as being a diplomatic mission to the country in which it is situated, it may also be a non-resident permanent mission to one or more other countries. There are thus resident and non-resident embassies.
A permanent diplomatic mission is typically known as an Embassy, and the head of the mission is known as an Ambassador, or High Commissioner. The term "embassy" is commonly used also as a section of a building in which the work of the diplomatic mission is carried out, but, strictly speaking, it is the diplomatic delegation itself that is the embassy, while the office space and the diplomatic work done is called the Chancery. Therefore, the Embassy operates in the Chancery.
The members of a diplomatic mission can reside within or outside the building that holds the mission's chancery, and their private residences enjoy the same rights as the premises of the mission as regards inviolability and protection.
All missions to the United Nations are known simply as permanent missions, while EU Member States' missions to the European Union are known as permanent representations and the head of such a mission is typically both a permanent representative and an ambassador. European Union missions abroad are known as EU delegations. Some countries have more particular naming for their missions and staff: a Vatican mission is headed by a nuncio (Latin "envoy") and consequently known as an apostolic nunciature. Under the rule of Muammar Gaddafi, Libya's missions used the name "people's bureau" and the head of the mission was a secretary.