IDPs: Internally Displaced Persons. Like refugees, except they have left their homes but remained in their country of citizenship.
NFIs: Non-food items, usually provided in a package to refugees or displaced people – things like pots and pans, clothing, soap, towels, or firewood.
OCHA: The UN Office for the Coordination of Humanitarian Affairs, the UN secretariat responsible for emergency response. Other agencies, especially UNHCR and the World Food Programme are involved in humanitarian response, but OCHA is supposed to keep them all aligned and cooperating.
OFDA: USAID’s Office of Foreign Disaster Assistance. It is the emergency arm of USAID, providing rapid funding and assessments in emergencies.
Sphere Guidelines: The Sphere Handbook defines minimum acceptable standards for the treatment of people in emergencies. It tells you things like how much water must be provided every day, how big tents have to be, and how many people can share a toilet.