A refugee is a person who flees across political borders (but not always) because of push factors.
A push factor is something that pushes people to leave their country and move somewhere else. According to international refugee law, a refugee is someone who seeks refuge in a foreign country because of war and violence, or out of fear of persecution "on account of race, religion, nationality, political opinion, or membership in a particular social group
As of December 31, 2005, the largest source countries of refugees are the Afghanistan, Iraq, Myanmar, Sudan, and the Palestinian Territories. The country with the largest number of IDPs (Internationally Displaced Person) is Sudan, with over 5 million. According to UNHCR (United Nations High Commissioner for Refugees) estimates, over 4.7 million Iraqis have had to leave their country since the US-led invasion of Iraq in 2003, with 2.7 million within Iraq and 2 million in neighboring countries. At least 60,000 Iraqis are losing their homes and becoming refugees every month.
Push Factor:
•War – can be with another country or a civil war.
-Examples of civil war would be Rwanda, who lost over 2.3 million people due to the genocide in 1994. Those 2.3 million people fled to neighboring countries and in 2004 many finally returned home.
-Owing to a well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group, or political opinion, is outside the country of their nationality, and is unable to or, owing to such fear, is unwilling to avail him/herself of the protection of that country
•Environmental Problems – such as famine or drought
•Natural Disasters – Such as tornados, hurricanes, tsunamis, earthquakes, etc.
-A good example of natural disaster refugees that did not leave their own country would be of here in the United States. Hurricane Katrina refugees went to other states across the country to seek shelter and receive help after the disaster.

Related terms:
Boat people - The term "boat people" came into common use in the 1970s with the mass exodus of Vietnamese refugees following the Vietnam War. It is a widely used form of migration for people migrating from Cuba, Haiti, Morocco, Vietnam or Albania. They often risk their lives on dangerously crude and overcrowded boats to escape oppression or poverty in their home nations. Events resulting from the Vietnam War led many people in Cambodia, Laos, and especially Vietnam to become refugees in the late 1970s and 1980s. The main danger to a boat person is that the boat he or she is sailing in may actually be anything that floats and is large enough for passengers. Although such makeshift craft can result in tragedy, some result in success. Boat people are frequently a source of controversy in the nation they seek to immigrate to, such as the United States, Canada, Italy, Spain and Australia.
Asylum seekers - Refugees are a subgroup of the broader category of displaced persons. Environmental refugees (people displaced because of environmental problems such as drought) are not included in the definition of "refugee" under international law, as well as internally displaced people. A claim for asylum may also be made onshore, usually after making an unauthorized arrival. Some governments are relatively tolerant and accepting of onshore asylum claims; other governments will not only refuse such claims, but may actually arrest or detain those who attempt to seek asylum
A displaced person (sometimes abbreviated DP) is a person who has been forced to leave his or her native place, a phenomenon known as forced migration