Short answers, pulled from the story.
Human migration is the movement of people from one place to another with the intention of settling, permanently or temporarily, at a new location. While external migration crosses national borders, internal migration within a single country is the dominant form of human migration globally.
A migrant is a person who changes their country of residence for general reasons such as better job opportunities or healthcare needs. The UNHCR defines a refugee as a person forced to flee their country because of violence or persecution. An asylum seeker leaves unwillingly but not under conditions of war or death threats, and becomes a refugee if their formal request for shelter is approved.
The number of international migrants rose from about 84 million in 1970, or 2.3% of the world's population, to more than 280 million in 2020, or 3.6%. Despite this growth, the share of migrants in the world population has stayed close to 3 percent over the last five decades.
Push factors are unfavorable aspects of a person's home area, such as war, famine, lack of jobs, persecution, and natural disasters. Pull factors are attractive aspects of a destination, such as job opportunities, better medical care, education, security, and family links. Demographer Everett S. Lee built his model of migration around this push and pull division.
In 2015, migrants made up 3.3% of the world's population but contributed 9.4% of global GDP. A 2021 Boston Consulting Group survey found 72% of more than 850 executives believed migration benefited their countries, and the Centre for Global Development estimated that opening all borders could add $78 trillion to world GDP.
Neoclassical economic theory attributes labour migration to wage differences between locations. Dual labour market theory points to pull from a secondary, low-skilled labour market in developed countries. The new economics of labor migration focuses on households using migration for risk aversion, while world-systems theory and osmosis theory examine migration on a global scale.
Migration governance has historically remained with individual states and tied to state sovereignty. Key treaties include the 1966 International Covenant on Civil and Political Rights and the 1951 Convention Relating to the Status of Refugees. The Global Compact for Safe, Orderly and Regular Migration was adopted by consensus in December 2018 and carried in the General Assembly by a vote of 152 to 5 with 12 abstentions.