A more thorough explanation:

Legal separation is a situation where a married couple decides to live apart but remain legally married. This can happen when both parties agree or when a judge orders it. People may choose to legally separate for religious reasons or to keep certain benefits like health or life insurance.

In terms of immigration, legal separation can be defined in two ways. The first is a narrow definition where legal separation means a limited or absolute divorce through a court process. This means that the marital status has been terminated. The second is a broader definition where legal separation requires some formal government action to dissolve or alter the marital relationship by law. In both cases, some kind of government action is needed to legally separate.

For example, if a couple decides to legally separate through a court process, they will need to get a divorce decree. This will officially end their marriage and allow them to live separately. In immigration court, legal separation can be important because a child's citizenship may depend on the marital status of their parents. If the parents are legally separated, it can affect the child's citizenship status.