Short answers, pulled from the story.
UNEP was established in 1972 following the United Nations Conference on the Human Environment, known as the Stockholm Conference. It was created by General Assembly Resolution 2997 and began operations with a staff of 300 and a five-year fund of more than $100 million.
UNEP is headquartered in Nairobi, Kenya. Nairobi was chosen over Geneva and other cities, making UNEP the first international organization to be based in the Global South.
Maurice Strong was elected unanimously by the UN General Assembly in December 1972 as UNEP's first executive director. He served from 1972 to 1975 and had also served as secretary-general of the 1972 Stockholm Conference that created the organization.
UNEP's most widely acclaimed success is the 1987 Montreal Protocol, a historic international agreement to protect the ozone layer by limiting emissions of gases blamed for thinning it. The protocol was negotiated under executive director Mostafa Kamal Tolba, who led UNEP from 1975 to 1992.
The United Nations Environment Assembly is UNEP's governing body, created in 2012 to replace the earlier Governing Council. It has 193 members and meets every two years, with its first session held in Nairobi in June 2014.
UNEP hosts the secretariats for the Convention on Biological Diversity, the Minamata Convention on Mercury, the Basel, Rotterdam and Stockholm Conventions, the Convention on Migratory Species, and CITES. In 1988, UNEP also co-founded the Intergovernmental Panel on Climate Change together with the World Meteorological Organization.