What is immigration supervision? What's the point?

"Immigration supervisor" is a vivid metaphor. For example, if you want to immigrate, you have to go to prison. You can't leave the country you want to emigrate for a long time (short term), because if you leave for a long time, you can't apply for naturalization or lose your immigration status.

Every immigration country has different immigration policies. Some countries need immigration supervision, while others don't. For example, the Canadian Immigration Service requires that permanent residents (maple leaf card holders, equivalent to American green cards) must live for two years within five years after obtaining an immigrant visa to retain their permanent resident status. However, European countries generally have no immigration supervision, so some domestic investors are more willing to immigrate to European countries, immigrate rather than move, and continue to operate their business in China.