What does it mean to sit in an immigration prison?

Immigration supervision 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. One refers to the time you have to live in another country in order to retain your immigration status. The other refers to the time you have to live in order to become a citizen. Immigration prisons are often nicknamed "immigrant prisoners". In fact, an immigration prison is not a prison, and sitting in an immigration prison does not put you in prison. It is only because it restricts the freedom of immigrants to a certain extent that it is called this name. Like Australia and Canada, permanent residence also has certain residence restrictions. For example, Canada requires that you must live for two years every five years before you can change your maple leaf card; However, there is a special exception. As long as you have permanent residency in New Zealand, you can go back whenever you want. The industry calls it a "permanent visa".