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. (source)