Final answer:
Emigration is when individuals leave a population, reducing its size, while immigration is when individuals join a population, increasing its size. Both are central to understanding population changes and can be voluntary, involuntary, or forced.
Step-by-step explanation:
Emigration happens when individuals move out of a population, while immigration happens when individuals move into a population. Emigration is the act of leaving one's country or region with the intent to settle permanently in another, and it often causes a decrease in population size and growth rate. In contrast, immigration is the migration of individuals into a population from other areas, which contributes to an increase in the population size and growth rate.
Human migration includes voluntary movements such as those looking for job opportunities, study abroad programs, or those initiated by personal desire to experience different parts of the world. There are also involuntary movements due to evacuations from war-torn regions, as well as forced migrations, like those experienced by many Native American tribes. Understanding the flow of people into and out of a country is crucial for analyzing population growth and demographic changes.