What does the immigration law do?
what are some reasons why it's important?

Immigration laws are designed to limit the number of workers entering the country so that there is not a surplus of workers. When there are more workers, there are fewer jobs available for citizens already within the country.

Why is it important? Immigrants boost America's economic growth and raise the general productivity of American workers by providing much-needed skills. Immigrant workers allow important sectors of the economy to expand, attracting investment and creating employment opportunities for native-born Americans.