Why do some people go to Hong Kong for fake marriage? What does fake marriage mean?

People come to Hong Kong for fake marriage to immigrate to Hong Kong, because they can live in Hong Kong after five years of marriage. During this five-year period, they can also apply for a visit to Hong Kong for three months, and because they come back every three months to renew their contracts, they can basically stay in Hong Kong for a long time. Fake marriage means that some people want to live in Hong Kong but can't find a legal way. They want to use money to ask the client to find the opposite sex who is willing to marry him for money, and then divorce him after he gets the Hong Kong identity card.