Habitual residence refers to the legal and factual relationship between a person and a country. It is a legal term and it can sometimes be difficult to pin down where a person is habitually resident. Literally it means, where a person resides as a matter of habit.
A person can only have one habitual residence anywhere in the world at any one time. It is the country in which a person has a fixed centre of interest and a settled intent to stay in that country. It should be distinguished from ordinary or simple residence of which a person can have two or more in parallel. Admitting habitual residence can carry tax and immigration consequences so care is needed. If in doubt, legal advice should be taken.